States with a majority of interstates renumbered?

[US 89]

Something I just noticed: three out of Idaho's five interstates have been renumbered at some point (15W --> 86, 80N --> 84, 180(N) --> 184). That's over half of the state's interstate highways.

Is there any other state with such a high proportion of renumbered interstates?

[Alps]

Pennsylvania has 14/23 (I'll allow that only 12 of the 14 were Interstates):
i-70: was 70S
i-76: was 80S
i-79: was 179 northern end
i-78, 80, 81, 83, 84, 90, 95: no
i-86: was PA 17
i-99: was US 220
176: was 180
180: no
276: was 280
279: was 79
283: no
295: was 95
376: was so many other things
380: was 81E
476: was PA 9, I-480
579: was 479
676: was 76/80S

[Max Rockatansky]

Some off the top of my head for California:

I-5W:  Became; I-580 and I-505 on the segments that weren't multiplexed with I-80.
I-880:  Became I-80.
I-15E:  Became I-215.
I-80:  In Sacramento became partially FHWA I-305.

[jp the roadgeek]

For CT:

I-84: Portion from East Hartford-Sturbridge was once CT 15, then I-84/CT 15 (with US 6 and US 44 piggybacking on portions), then I-86/CT 15, then just plain old I-86 when CT 15 was truncated (the US 44 piggyback was removed in 1982) then I-84 returned in 1984.  I-84 number was used on what is now I-384 (east of Exit 1) and US 6 Willimantic Bypass from 1968-1984.

I-291: Was CT 291 until the portion from US 5 to I-84 was completed in 1994.  Was the number for a much longer Hartford beltway, only parts of which have been completed.  The other completed portion is now the northern portion of CT 9.

I-384: Was once proposed as I-82, and to extend to Providence.  82 was changed to 84, and the numbered 84 was changed to 86.  84 shields did exist on the completed portion (east of Exit 1) until 1984, when 84 to Providence was cancelled and returned to I-86.

I-395: Once CT/MA 52.  Was planned to become I-290, but there was opposition to a 3di existing in a state where its parent didn't, so 395 was chosen.

I-684: NYSDOT originally routed I-87 on it, then multiplexed it with I-84 to Newburgh before joining the Thruway.  Eventually, the number was moved to the Thruway and I-684 was born

I-691: Originally US 6A in its infancy before being demoted to a state route (CT 66).  Only became an interstate in 1988 when it was completed to I-84; the CT 66 designation was truncated to I-91 and CT 322 was extended over the orphaned non-freeway portion of CT 66 in Southington and Cheshire.

[TheStranger]

Some off the top of my head for California:

I-5W:  Became; I-580 and I-505 on the segments that weren't multiplexed with I-80.
I-880:  Became I-80.
I-15E:  Became I-215.
I-80:  In Sacramento became partially FHWA I-305.

Some other ones:
I-280 and I-680 along Route 17 in San Jose - became, about 19 years later, I-880
(planned) I-180 along Route 17 in Richmond/San Rafael - became I-580 due to CalTrans not wanting to renumber 1934-present Route 180.  (Which also arguably led to the I-238 situation)
If Route 99 ever becomes interstate between Wheeler Ridge and Sacramento, that routing was planned pre-1958 to be I-5 or I-5E.  (Not sure if I-205 was former I-5W in planning, based on how one interprets the current Route 132 expressway originally planned as I-5W in Modesto)
Does the former unsigned I-110 between US 101 and I-5 (along former US 60/70/99) becoming part of the legislative definition of Route 10 count?

[kurumi]

For CT:

I-84: Portion from East Hartford-Sturbridge was once CT 15, then I-84/CT 15 (with US 6 and US 44 piggybacking on portions), then I-86/CT 15, then just plain old I-86 when CT 15 was truncated (the US 44 piggyback was removed in 1982) then I-84 returned in 1984.  I-84 number was used on what is now I-384 (east of Exit 1) and US 6 Willimantic Bypass from 1968-1984.

I-291: Was CT 291 until the portion from US 5 to I-84 was completed in 1994.  Was the number for a much longer Hartford beltway, only parts of which have been completed.  The other completed portion is now the northern portion of CT 9.

I-384: Was once proposed as I-82, and to extend to Providence.  82 was changed to 84, and the numbered 84 was changed to 86.  84 shields did exist on the completed portion (east of Exit 1) until 1984, when 84 to Providence was cancelled and returned to I-86.

I-395: Once CT/MA 52.  Was planned to become I-290, but there was opposition to a 3di existing in a state where its parent didn't, so 395 was chosen.

I-684: NYSDOT originally routed I-87 on it, then multiplexed it with I-84 to Newburgh before joining the Thruway.  Eventually, the number was moved to the Thruway and I-684 was born

I-691: Originally US 6A in its infancy before being demoted to a state route (CT 66).  Only became an interstate in 1988 when it was completed to I-84; the CT 66 designation was truncated to I-91 and CT 322 was extended over the orphaned non-freeway portion of CT 66 in Southington and Cheshire.

If we look at smaller portions, even parts of I-91 (segments in Hartford and Windsor were formerly US 5A) and I-95 (Darien bypass was US 1) were renumbered.

[ethanhopkin14]

Fun game.  In Texas:

Metroplex: I-20 became I-30

I-20 east of Dallas got downgraded to US 80 only and Texas Spur 557.

I-635 south quadrant became I-20

I-820 south quadrant became I-20

I-69 from Calallen to Robstown became I-69E

Future I-37 between mile marker 14 and 17 will be renumber I-37 and I-69E.  Maybe doesn't count?

[TheStranger]

Some off the top of my head for California:

I-5W:  Became; I-580 and I-505 on the segments that weren't multiplexed with I-80.
I-880:  Became I-80.
I-15E:  Became I-215.
I-80:  In Sacramento became partially FHWA I-305.

Some other ones:
I-280 and I-680 along Route 17 in San Jose - became, about 19 years later, I-880
(planned) I-180 along Route 17 in Richmond/San Rafael - became I-580 due to CalTrans not wanting to renumber 1934-present Route 180.  (Which also arguably led to the I-238 situation)
If Route 99 ever becomes interstate between Wheeler Ridge and Sacramento, that routing was planned pre-1958 to be I-5 or I-5E.  (Not sure if I-205 was former I-5W in planning, based on how one interprets the current Route 132 expressway originally planned as I-5W in Modesto)
Does the former unsigned I-110 between US 101 and I-5 (along former US 60/70/99) becoming part of the legislative definition of Route 10 count?

Piggybacking on Kurumi and jp the roadgeek's replies re: Connecticut (routes that were originally something else and then renumbered to interstate), here's a list of those in California:

- I-280 includes former US 101 between Route 82 in San Francisco and the Alemany Maze.  The segment of 280 between I-880 and US 101 was briefly planned as part of Route 17

I-280 east of US 101 to Cesar Chavez (Army) Street was part of Route 82 1964-1968; the portion between Cesar Chavez to the current 5th Street north terminus and the unbuilt portion to I-80/I-480 was originally part of the 1964-1968 northern extent of Route 87, before becoming added to the 280 route.

The Route 1 freeway from I-280 in Daly City to Font Boulevard in SF was slated to be part of the original planned (1950s-1968) I-280.

- I-680 supplanted former Route 21 between Benicia and Cordelia (and approximated the Route 21 corridor from Concord southwards).  The portion south of Route 262 was briefly proposed as Route 17.

(Route 262 itself was part of the definition of I-680 at one point)

- I-880 is notably former Route 17 as well as former I-680/I-280 on the southern terminus.  While the Cypress Viaduct portion of I-880 has been replaced for the last 23 years with the West Oakland railway ROW alignment, the viaduct once also held Business US 50

- I-80 in California is mostly former US 40 except for former I-880 in Sacramento.  The Central Freeway was once planned (along the pre-2005 Fell Street to Bayshore Freeway segment) as a US 101/I-80 concurrency, as part of the never-built Western Freeway project, and some signage hinting at that did exist on I-80 west along the Skyway in San Francisco prior to about 1994.  (Could even argue that today's I-80/US 101 FREEWAY ENTRANCE sign at Market/Octavia hints back at this too)  I-80 between US 101 and the MacArthur Maze was once US 50.  Former I-80 (now US 50/unsigned I-305, was Business 80 for years) in West Sacramento was US 40/US 99W, and former I-80 in Midtown/Arden, now Business 80/unsigned Route 51, was US 99E and partially US 40.

- I-5 south of Boyle Heights was entirely US 101., and supplanted an old Bypass US 101 which itself took over parts of former pre-1959 Route 10.

- I-10 east of US 101 was entirely US 70 and mostly US 60, and partially US 99.

- I-215 supplanted the 1950s-1968 I-15 between Devore and Colton, and the 1974-1982 I-15E along its entire route.  All of 215 used to be US 395, with the portion north of Riverside also US 91 and the portion from San Bernardino north as US 66.

- I-405 from LAX north towards Sepulveda Pass was built as Route 7.

- I-5 between Wheeler Ridge and I-10 was originally built as US 99 with US 6 running along the Sylmar-Echo Park segment.  I-5 north of Red Bluff also had segments built as US 99 as well.

- I-15 in San Diego south of Route 163 was originally Route 103, I think someone here said that was signed briefly.  I-15 north of Route 163 up to Temecula and from Devore to the Nevada border was all US 395, with the portion from Devore to Barstow also carrying US 66 and US 91 and the Barstow-Nevada portion carrying US 466.  (Former I-15 parallel to the current freeway at the Miramar MCAS was originally US 395, the existing freeway there however never was 395 at any point.)

I-15 between Temecula and Corona took over old Route 71 though mostly on a parallel alignment, and I-15 between Route 91 and Devore supplanted the parallel temporary Route 31.

- I-8 east of I-5 was US 80, while I-8 west of I-5 was Route 109.

- I-110/Harbor Freeway was originally US 6/Route 11, and I-710/Long Beach Freeway was Route 15 prior to 1964, then Route 7 from 1964-1984.

- I-980 in Oakland was originally a part of Route 24 legislatively, not sure if this was signed.

- I-580 in the East Bay was built as US 50 (and I-5W as mentioned earlier).  I-580 from Albany to San Rafael had been Route 17 (could argue the same for the Berkeley 580/80 concurrency, which originally was US 40/Route 17).

- I-238 used to be state route 238 though I've never seen photos of it in pre-Interstate garb.  I don't think this portion of 238 was ever Route 9.

- Route 57 between Glendora and the Kellogg Interchange is former I-210, before State Route 210 was established from Glendora east to Redlands.

- The freeway portion of US 101 in the Presidio east of Route 1 had been part of the proposed I-480, and the freeway portion of Route 1 in the Presidio had been part of the original I-280 proposals pre-1968.

- The Route 132 expressway being constructed now in Modesto was originally planned as I-5W.

- I-380 in San Bruno was originally proposed in the late sixties as Route 186.

- I-105 near LAX was originally legislatively part of State Route 42, though never signed as such as the parallel Firestone Boulevard route (pre-1959 Route 10) remained part of 42 even as 105 was being constructed.

- Portions of I-40 are former US 66, particularly right in Barstow at I-15.

[TheGrassGuy]

Pennsylvania has 14/23 (I'll allow that only 12 of the 14 were Interstates):
i-70: was 70S
i-76: was 80S
i-79: was 179 northern end
i-78, 80, 81, 83, 84, 90, 95: no
i-86: was PA 17
i-99: was US 220
176: was 180
180: no
276: was 280
279: was 79
283: no
295: was 95
376: was so many other things
380: was 81E
476: was PA 9, I-480
579: was 479
676: was 76/80S

How was 276 280? You're also overlooking the 95 interchange.

[cl94]

Pennsylvania has 14/23 (I'll allow that only 12 of the 14 were Interstates):
i-70: was 70S
i-76: was 80S
i-79: was 179 northern end
i-78, 80, 81, 83, 84, 90, 95: no
i-86: was PA 17
i-99: was US 220
176: was 180
180: no
276: was 280
279: was 79
283: no
295: was 95
376: was so many other things
380: was 81E
476: was PA 9, I-480
579: was 479
676: was 76/80S

How was 276 280? You're also overlooking the 95 interchange.

76 was once 80S. Under this numbering, 276 was 280 because it was a child of 80S.

[SkyPesos]

With the 2 states I'm familiar with, it's almost the same numbers as day one, but there's still 1 in each

OH: I-76 used to be I-80S. Not really a renumbering, but I-490 was originally planned as a section of the longer I-290.
MO: The first 20 miles of I-270 was first designated as I-244. MoDot wanted 144 for it first, but got changed to an even first digit because of its partial beltway status.

[ethanhopkin14]

Some off the top of my head for California:

I-5W:  Became; I-580 and I-505 on the segments that weren't multiplexed with I-80.
I-880:  Became I-80.
I-15E:  Became I-215.
I-80:  In Sacramento became partially FHWA I-305.

Some other ones:
I-280 and I-680 along Route 17 in San Jose - became, about 19 years later, I-880
(planned) I-180 along Route 17 in Richmond/San Rafael - became I-580 due to CalTrans not wanting to renumber 1934-present Route 180.  (Which also arguably led to the I-238 situation)
If Route 99 ever becomes interstate between Wheeler Ridge and Sacramento, that routing was planned pre-1958 to be I-5 or I-5E.  (Not sure if I-205 was former I-5W in planning, based on how one interprets the current Route 132 expressway originally planned as I-5W in Modesto)
Does the former unsigned I-110 between US 101 and I-5 (along former US 60/70/99) becoming part of the legislative definition of Route 10 count?

Piggybacking on Kurumi and jp the roadgeek's replies re: Connecticut (routes that were originally something else and then renumbered to interstate), here's a list of those in California:

- I-280 includes former US 101 between Route 82 in San Francisco and the Alemany Maze.  The segment of 280 between I-880 and US 101 was briefly planned as part of Route 17

I-280 east of US 101 to Cesar Chavez (Army) Street was part of Route 82 1964-1968; the portion between Cesar Chavez to the current 5th Street north terminus and the unbuilt portion to I-80/I-480 was originally part of the 1964-1968 northern extent of Route 87, before becoming added to the 280 route.

The Route 1 freeway from I-280 in Daly City to Font Boulevard in SF was slated to be part of the original planned (1950s-1968) I-280.

- I-680 supplanted former Route 21 between Benicia and Cordelia (and approximated the Route 21 corridor from Concord southwards).  The portion south of Route 262 was briefly proposed as Route 17.

(Route 262 itself was part of the definition of I-680 at one point)

- I-880 is notably former Route 17 as well as former I-680/I-280 on the southern terminus.  While the Cypress Viaduct portion of I-880 has been replaced for the last 23 years with the West Oakland railway ROW alignment, the viaduct once also held Business US 50

- I-80 in California is mostly former US 40 except for former I-880 in Sacramento.  The Central Freeway was once planned (along the pre-2005 Fell Street to Bayshore Freeway segment) as a US 101/I-80 concurrency, as part of the never-built Western Freeway project, and some signage hinting at that did exist on I-80 west along the Skyway in San Francisco prior to about 1994.  (Could even argue that today's I-80/US 101 FREEWAY ENTRANCE sign at Market/Octavia hints back at this too)  I-80 between US 101 and the MacArthur Maze was once US 50.  Former I-80 (now US 50/unsigned I-305, was Business 80 for years) in West Sacramento was US 40/US 99W, and former I-80 in Midtown/Arden, now Business 80/unsigned Route 51, was US 99E and partially US 40.

- I-5 south of Boyle Heights was entirely US 101., and supplanted an old Bypass US 101 which itself took over parts of former pre-1959 Route 10.

- I-10 east of US 101 was entirely US 70 and mostly US 60, and partially US 99.

- I-215 supplanted the 1950s-1968 I-15 between Devore and Colton, and the 1974-1982 I-15E along its entire route.  All of 215 used to be US 395, with the portion north of Riverside also US 91 and the portion from San Bernardino north as US 66.

- I-405 from LAX north towards Sepulveda Pass was built as Route 7.

- I-5 between Wheeler Ridge and I-10 was originally built as US 99 with US 6 running along the Sylmar-Echo Park segment.  I-5 north of Red Bluff also had segments built as US 99 as well.

- I-15 in San Diego south of Route 163 was originally Route 103, I think someone here said that was signed briefly.  I-15 north of Route 163 up to Temecula and from Devore to the Nevada border was all US 395, with the portion from Devore to Barstow also carrying US 66 and US 91 and the Barstow-Nevada portion carrying US 466.  (Former I-15 parallel to the current freeway at the Miramar MCAS was originally US 395, the existing freeway there however never was 395 at any point.)

I-15 between Temecula and Corona took over old Route 71 though mostly on a parallel alignment, and I-15 between Route 91 and Devore supplanted the parallel temporary Route 31.

- I-8 east of I-5 was US 80, while I-8 west of I-5 was Route 109.

- I-110/Harbor Freeway was originally US 6/Route 11, and I-710/Long Beach Freeway was Route 15 prior to 1964, then Route 7 from 1964-1984.

- I-980 in Oakland was originally a part of Route 24 legislatively, not sure if this was signed.

- I-580 in the East Bay was built as US 50 (and I-5W as mentioned earlier).  I-580 from Albany to San Rafael had been Route 17 (could argue the same for the Berkeley 580/80 concurrency, which originally was US 40/Route 17).

- I-238 used to be state route 238 though I've never seen photos of it in pre-Interstate garb.  I don't think this portion of 238 was ever Route 9.

- Route 57 between Glendora and the Kellogg Interchange is former I-210, before State Route 210 was established from Glendora east to Redlands.

- The freeway portion of US 101 in the Presidio east of Route 1 had been part of the proposed I-480, and the freeway portion of Route 1 in the Presidio had been part of the original I-280 proposals pre-1968.

- The Route 132 expressway being constructed now in Modesto was originally planned as I-5W.

- I-380 in San Bruno was originally proposed in the late sixties as Route 186.

- I-105 near LAX was originally legislatively part of State Route 42, though never signed as such as the parallel Firestone Boulevard route (pre-1959 Route 10) remained part of 42 even as 105 was being constructed.

- Portions of I-40 are former US 66, particularly right in Barstow at I-15.

I think the OP was referring specifically to instances where a highway was Interstate X, then renumbered Interstate Y.  The list of highways that were sub-interstate that are now interstate is as long as the list of interstates, and we can play that game forever.  Yes, it's interesting and I like it, but I think the topic was specifically renumbered interstates. 

[roadman65]

Florida had part of Interstate 275 two different numbers across the Howard Franklin Bridge. First I-4, then I-75, and now 275.

I-275 from Downtown Tampa to Wesley Chapel was I-75 and now I-275.


In Texas I-69E near Robstown was I-69 for a brief moment, but a very short stint.
I-30 between its western end and US 80 was I-20 in the days of the DFW Turnpike.
US 190 now is I-14.

In Arkansas I-540 became I-49 north of I-40.
US 63 became I-555.
AR 549 became I-49 also due to its not yet connected to the system.

[TheStranger]

Some off the top of my head for California:

I-5W:  Became; I-580 and I-505 on the segments that weren't multiplexed with I-80.
I-880:  Became I-80.
I-15E:  Became I-215.
I-80:  In Sacramento became partially FHWA I-305.

Some other ones:
I-280 and I-680 along Route 17 in San Jose - became, about 19 years later, I-880
(planned) I-180 along Route 17 in Richmond/San Rafael - became I-580 due to CalTrans not wanting to renumber 1934-present Route 180.  (Which also arguably led to the I-238 situation)
If Route 99 ever becomes interstate between Wheeler Ridge and Sacramento, that routing was planned pre-1958 to be I-5 or I-5E.  (Not sure if I-205 was former I-5W in planning, based on how one interprets the current Route 132 expressway originally planned as I-5W in Modesto)
Does the former unsigned I-110 between US 101 and I-5 (along former US 60/70/99) becoming part of the legislative definition of Route 10 count?

Piggybacking on Kurumi and jp the roadgeek's replies re: Connecticut (routes that were originally something else and then renumbered to interstate), here's a list of those in California:

- I-280 includes former US 101 between Route 82 in San Francisco and the Alemany Maze.  The segment of 280 between I-880 and US 101 was briefly planned as part of Route 17

I-280 east of US 101 to Cesar Chavez (Army) Street was part of Route 82 1964-1968; the portion between Cesar Chavez to the current 5th Street north terminus and the unbuilt portion to I-80/I-480 was originally part of the 1964-1968 northern extent of Route 87, before becoming added to the 280 route.

The Route 1 freeway from I-280 in Daly City to Font Boulevard in SF was slated to be part of the original planned (1950s-1968) I-280.

- I-680 supplanted former Route 21 between Benicia and Cordelia (and approximated the Route 21 corridor from Concord southwards).  The portion south of Route 262 was briefly proposed as Route 17.

(Route 262 itself was part of the definition of I-680 at one point)

- I-880 is notably former Route 17 as well as former I-680/I-280 on the southern terminus.  While the Cypress Viaduct portion of I-880 has been replaced for the last 23 years with the West Oakland railway ROW alignment, the viaduct once also held Business US 50

- I-80 in California is mostly former US 40 except for former I-880 in Sacramento.  The Central Freeway was once planned (along the pre-2005 Fell Street to Bayshore Freeway segment) as a US 101/I-80 concurrency, as part of the never-built Western Freeway project, and some signage hinting at that did exist on I-80 west along the Skyway in San Francisco prior to about 1994.  (Could even argue that today's I-80/US 101 FREEWAY ENTRANCE sign at Market/Octavia hints back at this too)  I-80 between US 101 and the MacArthur Maze was once US 50.  Former I-80 (now US 50/unsigned I-305, was Business 80 for years) in West Sacramento was US 40/US 99W, and former I-80 in Midtown/Arden, now Business 80/unsigned Route 51, was US 99E and partially US 40.

- I-5 south of Boyle Heights was entirely US 101., and supplanted an old Bypass US 101 which itself took over parts of former pre-1959 Route 10.

- I-10 east of US 101 was entirely US 70 and mostly US 60, and partially US 99.

- I-215 supplanted the 1950s-1968 I-15 between Devore and Colton, and the 1974-1982 I-15E along its entire route.  All of 215 used to be US 395, with the portion north of Riverside also US 91 and the portion from San Bernardino north as US 66.

- I-405 from LAX north towards Sepulveda Pass was built as Route 7.

- I-5 between Wheeler Ridge and I-10 was originally built as US 99 with US 6 running along the Sylmar-Echo Park segment.  I-5 north of Red Bluff also had segments built as US 99 as well.

- I-15 in San Diego south of Route 163 was originally Route 103, I think someone here said that was signed briefly.  I-15 north of Route 163 up to Temecula and from Devore to the Nevada border was all US 395, with the portion from Devore to Barstow also carrying US 66 and US 91 and the Barstow-Nevada portion carrying US 466.  (Former I-15 parallel to the current freeway at the Miramar MCAS was originally US 395, the existing freeway there however never was 395 at any point.)

I-15 between Temecula and Corona took over old Route 71 though mostly on a parallel alignment, and I-15 between Route 91 and Devore supplanted the parallel temporary Route 31.

- I-8 east of I-5 was US 80, while I-8 west of I-5 was Route 109.

- I-110/Harbor Freeway was originally US 6/Route 11, and I-710/Long Beach Freeway was Route 15 prior to 1964, then Route 7 from 1964-1984.

- I-980 in Oakland was originally a part of Route 24 legislatively, not sure if this was signed.

- I-580 in the East Bay was built as US 50 (and I-5W as mentioned earlier).  I-580 from Albany to San Rafael had been Route 17 (could argue the same for the Berkeley 580/80 concurrency, which originally was US 40/Route 17).

- I-238 used to be state route 238 though I've never seen photos of it in pre-Interstate garb.  I don't think this portion of 238 was ever Route 9.

- Route 57 between Glendora and the Kellogg Interchange is former I-210, before State Route 210 was established from Glendora east to Redlands.

- The freeway portion of US 101 in the Presidio east of Route 1 had been part of the proposed I-480, and the freeway portion of Route 1 in the Presidio had been part of the original I-280 proposals pre-1968.

- The Route 132 expressway being constructed now in Modesto was originally planned as I-5W.

- I-380 in San Bruno was originally proposed in the late sixties as Route 186.

- I-105 near LAX was originally legislatively part of State Route 42, though never signed as such as the parallel Firestone Boulevard route (pre-1959 Route 10) remained part of 42 even as 105 was being constructed.

- Portions of I-40 are former US 66, particularly right in Barstow at I-15.

I think the OP was referring specifically to instances where a highway was Interstate X, then renumbered Interstate Y.  The list of highways that were sub-interstate that are now interstate is as long as the list of interstates, and we can play that game forever.  Yes, it's interesting and I like it, but I think the topic was specifically renumbered interstates.

Your earlier example of I-20 in East Dallas becoming US 80 was kinda the template here but yeah I see where it is more about one interstate becoming another.

SM-G973U1

[ethanhopkin14]

Some off the top of my head for California:

I-5W:  Became; I-580 and I-505 on the segments that weren't multiplexed with I-80.
I-880:  Became I-80.
I-15E:  Became I-215.
I-80:  In Sacramento became partially FHWA I-305.

Some other ones:
I-280 and I-680 along Route 17 in San Jose - became, about 19 years later, I-880
(planned) I-180 along Route 17 in Richmond/San Rafael - became I-580 due to CalTrans not wanting to renumber 1934-present Route 180.  (Which also arguably led to the I-238 situation)
If Route 99 ever becomes interstate between Wheeler Ridge and Sacramento, that routing was planned pre-1958 to be I-5 or I-5E.  (Not sure if I-205 was former I-5W in planning, based on how one interprets the current Route 132 expressway originally planned as I-5W in Modesto)
Does the former unsigned I-110 between US 101 and I-5 (along former US 60/70/99) becoming part of the legislative definition of Route 10 count?

Piggybacking on Kurumi and jp the roadgeek's replies re: Connecticut (routes that were originally something else and then renumbered to interstate), here's a list of those in California:

- I-280 includes former US 101 between Route 82 in San Francisco and the Alemany Maze.  The segment of 280 between I-880 and US 101 was briefly planned as part of Route 17

I-280 east of US 101 to Cesar Chavez (Army) Street was part of Route 82 1964-1968; the portion between Cesar Chavez to the current 5th Street north terminus and the unbuilt portion to I-80/I-480 was originally part of the 1964-1968 northern extent of Route 87, before becoming added to the 280 route.

The Route 1 freeway from I-280 in Daly City to Font Boulevard in SF was slated to be part of the original planned (1950s-1968) I-280.

- I-680 supplanted former Route 21 between Benicia and Cordelia (and approximated the Route 21 corridor from Concord southwards).  The portion south of Route 262 was briefly proposed as Route 17.

(Route 262 itself was part of the definition of I-680 at one point)

- I-880 is notably former Route 17 as well as former I-680/I-280 on the southern terminus.  While the Cypress Viaduct portion of I-880 has been replaced for the last 23 years with the West Oakland railway ROW alignment, the viaduct once also held Business US 50

- I-80 in California is mostly former US 40 except for former I-880 in Sacramento.  The Central Freeway was once planned (along the pre-2005 Fell Street to Bayshore Freeway segment) as a US 101/I-80 concurrency, as part of the never-built Western Freeway project, and some signage hinting at that did exist on I-80 west along the Skyway in San Francisco prior to about 1994.  (Could even argue that today's I-80/US 101 FREEWAY ENTRANCE sign at Market/Octavia hints back at this too)  I-80 between US 101 and the MacArthur Maze was once US 50.  Former I-80 (now US 50/unsigned I-305, was Business 80 for years) in West Sacramento was US 40/US 99W, and former I-80 in Midtown/Arden, now Business 80/unsigned Route 51, was US 99E and partially US 40.

- I-5 south of Boyle Heights was entirely US 101., and supplanted an old Bypass US 101 which itself took over parts of former pre-1959 Route 10.

- I-10 east of US 101 was entirely US 70 and mostly US 60, and partially US 99.

- I-215 supplanted the 1950s-1968 I-15 between Devore and Colton, and the 1974-1982 I-15E along its entire route.  All of 215 used to be US 395, with the portion north of Riverside also US 91 and the portion from San Bernardino north as US 66.

- I-405 from LAX north towards Sepulveda Pass was built as Route 7.

- I-5 between Wheeler Ridge and I-10 was originally built as US 99 with US 6 running along the Sylmar-Echo Park segment.  I-5 north of Red Bluff also had segments built as US 99 as well.

- I-15 in San Diego south of Route 163 was originally Route 103, I think someone here said that was signed briefly.  I-15 north of Route 163 up to Temecula and from Devore to the Nevada border was all US 395, with the portion from Devore to Barstow also carrying US 66 and US 91 and the Barstow-Nevada portion carrying US 466.  (Former I-15 parallel to the current freeway at the Miramar MCAS was originally US 395, the existing freeway there however never was 395 at any point.)

I-15 between Temecula and Corona took over old Route 71 though mostly on a parallel alignment, and I-15 between Route 91 and Devore supplanted the parallel temporary Route 31.

- I-8 east of I-5 was US 80, while I-8 west of I-5 was Route 109.

- I-110/Harbor Freeway was originally US 6/Route 11, and I-710/Long Beach Freeway was Route 15 prior to 1964, then Route 7 from 1964-1984.

- I-980 in Oakland was originally a part of Route 24 legislatively, not sure if this was signed.

- I-580 in the East Bay was built as US 50 (and I-5W as mentioned earlier).  I-580 from Albany to San Rafael had been Route 17 (could argue the same for the Berkeley 580/80 concurrency, which originally was US 40/Route 17).

- I-238 used to be state route 238 though I've never seen photos of it in pre-Interstate garb.  I don't think this portion of 238 was ever Route 9.

- Route 57 between Glendora and the Kellogg Interchange is former I-210, before State Route 210 was established from Glendora east to Redlands.

- The freeway portion of US 101 in the Presidio east of Route 1 had been part of the proposed I-480, and the freeway portion of Route 1 in the Presidio had been part of the original I-280 proposals pre-1968.

- The Route 132 expressway being constructed now in Modesto was originally planned as I-5W.

- I-380 in San Bruno was originally proposed in the late sixties as Route 186.

- I-105 near LAX was originally legislatively part of State Route 42, though never signed as such as the parallel Firestone Boulevard route (pre-1959 Route 10) remained part of 42 even as 105 was being constructed.

- Portions of I-40 are former US 66, particularly right in Barstow at I-15.

I think the OP was referring specifically to instances where a highway was Interstate X, then renumbered Interstate Y.  The list of highways that were sub-interstate that are now interstate is as long as the list of interstates, and we can play that game forever.  Yes, it's interesting and I like it, but I think the topic was specifically renumbered interstates.

Your earlier example of I-20 in East Dallas becoming US 80 was kinda the template here but yeah I see where it is more about one interstate becoming another.

SM-G973U1

Fair enough.  I only mentioned it because it was an interstate that's not an interstate now, not the other way around. 

[roadman65]

Some off the top of my head for California:

I-5W:  Became; I-580 and I-505 on the segments that weren't multiplexed with I-80.
I-880:  Became I-80.
I-15E:  Became I-215.
I-80:  In Sacramento became partially FHWA I-305.

Some other ones:
I-280 and I-680 along Route 17 in San Jose - became, about 19 years later, I-880
(planned) I-180 along Route 17 in Richmond/San Rafael - became I-580 due to CalTrans not wanting to renumber 1934-present Route 180.  (Which also arguably led to the I-238 situation)
If Route 99 ever becomes interstate between Wheeler Ridge and Sacramento, that routing was planned pre-1958 to be I-5 or I-5E.  (Not sure if I-205 was former I-5W in planning, based on how one interprets the current Route 132 expressway originally planned as I-5W in Modesto)
Does the former unsigned I-110 between US 101 and I-5 (along former US 60/70/99) becoming part of the legislative definition of Route 10 count?

Piggybacking on Kurumi and jp the roadgeek's replies re: Connecticut (routes that were originally something else and then renumbered to interstate), here's a list of those in California:

- I-280 includes former US 101 between Route 82 in San Francisco and the Alemany Maze.  The segment of 280 between I-880 and US 101 was briefly planned as part of Route 17

I-280 east of US 101 to Cesar Chavez (Army) Street was part of Route 82 1964-1968; the portion between Cesar Chavez to the current 5th Street north terminus and the unbuilt portion to I-80/I-480 was originally part of the 1964-1968 northern extent of Route 87, before becoming added to the 280 route.

The Route 1 freeway from I-280 in Daly City to Font Boulevard in SF was slated to be part of the original planned (1950s-1968) I-280.

- I-680 supplanted former Route 21 between Benicia and Cordelia (and approximated the Route 21 corridor from Concord southwards).  The portion south of Route 262 was briefly proposed as Route 17.

(Route 262 itself was part of the definition of I-680 at one point)

- I-880 is notably former Route 17 as well as former I-680/I-280 on the southern terminus.  While the Cypress Viaduct portion of I-880 has been replaced for the last 23 years with the West Oakland railway ROW alignment, the viaduct once also held Business US 50

- I-80 in California is mostly former US 40 except for former I-880 in Sacramento.  The Central Freeway was once planned (along the pre-2005 Fell Street to Bayshore Freeway segment) as a US 101/I-80 concurrency, as part of the never-built Western Freeway project, and some signage hinting at that did exist on I-80 west along the Skyway in San Francisco prior to about 1994.  (Could even argue that today's I-80/US 101 FREEWAY ENTRANCE sign at Market/Octavia hints back at this too)  I-80 between US 101 and the MacArthur Maze was once US 50.  Former I-80 (now US 50/unsigned I-305, was Business 80 for years) in West Sacramento was US 40/US 99W, and former I-80 in Midtown/Arden, now Business 80/unsigned Route 51, was US 99E and partially US 40.

- I-5 south of Boyle Heights was entirely US 101., and supplanted an old Bypass US 101 which itself took over parts of former pre-1959 Route 10.

- I-10 east of US 101 was entirely US 70 and mostly US 60, and partially US 99.

- I-215 supplanted the 1950s-1968 I-15 between Devore and Colton, and the 1974-1982 I-15E along its entire route.  All of 215 used to be US 395, with the portion north of Riverside also US 91 and the portion from San Bernardino north as US 66.

- I-405 from LAX north towards Sepulveda Pass was built as Route 7.

- I-5 between Wheeler Ridge and I-10 was originally built as US 99 with US 6 running along the Sylmar-Echo Park segment.  I-5 north of Red Bluff also had segments built as US 99 as well.

- I-15 in San Diego south of Route 163 was originally Route 103, I think someone here said that was signed briefly.  I-15 north of Route 163 up to Temecula and from Devore to the Nevada border was all US 395, with the portion from Devore to Barstow also carrying US 66 and US 91 and the Barstow-Nevada portion carrying US 466.  (Former I-15 parallel to the current freeway at the Miramar MCAS was originally US 395, the existing freeway there however never was 395 at any point.)

I-15 between Temecula and Corona took over old Route 71 though mostly on a parallel alignment, and I-15 between Route 91 and Devore supplanted the parallel temporary Route 31.

- I-8 east of I-5 was US 80, while I-8 west of I-5 was Route 109.

- I-110/Harbor Freeway was originally US 6/Route 11, and I-710/Long Beach Freeway was Route 15 prior to 1964, then Route 7 from 1964-1984.

- I-980 in Oakland was originally a part of Route 24 legislatively, not sure if this was signed.

- I-580 in the East Bay was built as US 50 (and I-5W as mentioned earlier).  I-580 from Albany to San Rafael had been Route 17 (could argue the same for the Berkeley 580/80 concurrency, which originally was US 40/Route 17).

- I-238 used to be state route 238 though I've never seen photos of it in pre-Interstate garb.  I don't think this portion of 238 was ever Route 9.

- Route 57 between Glendora and the Kellogg Interchange is former I-210, before State Route 210 was established from Glendora east to Redlands.

- The freeway portion of US 101 in the Presidio east of Route 1 had been part of the proposed I-480, and the freeway portion of Route 1 in the Presidio had been part of the original I-280 proposals pre-1968.

- The Route 132 expressway being constructed now in Modesto was originally planned as I-5W.

- I-380 in San Bruno was originally proposed in the late sixties as Route 186.

- I-105 near LAX was originally legislatively part of State Route 42, though never signed as such as the parallel Firestone Boulevard route (pre-1959 Route 10) remained part of 42 even as 105 was being constructed.

- Portions of I-40 are former US 66, particularly right in Barstow at I-15.

I think the OP was referring specifically to instances where a highway was Interstate X, then renumbered Interstate Y.  The list of highways that were sub-interstate that are now interstate is as long as the list of interstates, and we can play that game forever.  Yes, it's interesting and I like it, but I think the topic was specifically renumbered interstates.

Your earlier example of I-20 in East Dallas becoming US 80 was kinda the template here but yeah I see where it is more about one interstate becoming another.

SM-G973U1

Think US 80 taking over I-20 and US 6 over I-84 are rare occurrences.  Even I-895 to NY 895 is not the same due to freeway downgrade there.

[ethanhopkin14]

Some off the top of my head for California:

I-5W:  Became; I-580 and I-505 on the segments that weren't multiplexed with I-80.
I-880:  Became I-80.
I-15E:  Became I-215.
I-80:  In Sacramento became partially FHWA I-305.

Some other ones:
I-280 and I-680 along Route 17 in San Jose - became, about 19 years later, I-880
(planned) I-180 along Route 17 in Richmond/San Rafael - became I-580 due to CalTrans not wanting to renumber 1934-present Route 180.  (Which also arguably led to the I-238 situation)
If Route 99 ever becomes interstate between Wheeler Ridge and Sacramento, that routing was planned pre-1958 to be I-5 or I-5E.  (Not sure if I-205 was former I-5W in planning, based on how one interprets the current Route 132 expressway originally planned as I-5W in Modesto)
Does the former unsigned I-110 between US 101 and I-5 (along former US 60/70/99) becoming part of the legislative definition of Route 10 count?

Piggybacking on Kurumi and jp the roadgeek's replies re: Connecticut (routes that were originally something else and then renumbered to interstate), here's a list of those in California:

- I-280 includes former US 101 between Route 82 in San Francisco and the Alemany Maze.  The segment of 280 between I-880 and US 101 was briefly planned as part of Route 17

I-280 east of US 101 to Cesar Chavez (Army) Street was part of Route 82 1964-1968; the portion between Cesar Chavez to the current 5th Street north terminus and the unbuilt portion to I-80/I-480 was originally part of the 1964-1968 northern extent of Route 87, before becoming added to the 280 route.

The Route 1 freeway from I-280 in Daly City to Font Boulevard in SF was slated to be part of the original planned (1950s-1968) I-280.

- I-680 supplanted former Route 21 between Benicia and Cordelia (and approximated the Route 21 corridor from Concord southwards).  The portion south of Route 262 was briefly proposed as Route 17.

(Route 262 itself was part of the definition of I-680 at one point)

- I-880 is notably former Route 17 as well as former I-680/I-280 on the southern terminus.  While the Cypress Viaduct portion of I-880 has been replaced for the last 23 years with the West Oakland railway ROW alignment, the viaduct once also held Business US 50

- I-80 in California is mostly former US 40 except for former I-880 in Sacramento.  The Central Freeway was once planned (along the pre-2005 Fell Street to Bayshore Freeway segment) as a US 101/I-80 concurrency, as part of the never-built Western Freeway project, and some signage hinting at that did exist on I-80 west along the Skyway in San Francisco prior to about 1994.  (Could even argue that today's I-80/US 101 FREEWAY ENTRANCE sign at Market/Octavia hints back at this too)  I-80 between US 101 and the MacArthur Maze was once US 50.  Former I-80 (now US 50/unsigned I-305, was Business 80 for years) in West Sacramento was US 40/US 99W, and former I-80 in Midtown/Arden, now Business 80/unsigned Route 51, was US 99E and partially US 40.

- I-5 south of Boyle Heights was entirely US 101., and supplanted an old Bypass US 101 which itself took over parts of former pre-1959 Route 10.

- I-10 east of US 101 was entirely US 70 and mostly US 60, and partially US 99.

- I-215 supplanted the 1950s-1968 I-15 between Devore and Colton, and the 1974-1982 I-15E along its entire route.  All of 215 used to be US 395, with the portion north of Riverside also US 91 and the portion from San Bernardino north as US 66.

- I-405 from LAX north towards Sepulveda Pass was built as Route 7.

- I-5 between Wheeler Ridge and I-10 was originally built as US 99 with US 6 running along the Sylmar-Echo Park segment.  I-5 north of Red Bluff also had segments built as US 99 as well.

- I-15 in San Diego south of Route 163 was originally Route 103, I think someone here said that was signed briefly.  I-15 north of Route 163 up to Temecula and from Devore to the Nevada border was all US 395, with the portion from Devore to Barstow also carrying US 66 and US 91 and the Barstow-Nevada portion carrying US 466.  (Former I-15 parallel to the current freeway at the Miramar MCAS was originally US 395, the existing freeway there however never was 395 at any point.)

I-15 between Temecula and Corona took over old Route 71 though mostly on a parallel alignment, and I-15 between Route 91 and Devore supplanted the parallel temporary Route 31.

- I-8 east of I-5 was US 80, while I-8 west of I-5 was Route 109.

- I-110/Harbor Freeway was originally US 6/Route 11, and I-710/Long Beach Freeway was Route 15 prior to 1964, then Route 7 from 1964-1984.

- I-980 in Oakland was originally a part of Route 24 legislatively, not sure if this was signed.

- I-580 in the East Bay was built as US 50 (and I-5W as mentioned earlier).  I-580 from Albany to San Rafael had been Route 17 (could argue the same for the Berkeley 580/80 concurrency, which originally was US 40/Route 17).

- I-238 used to be state route 238 though I've never seen photos of it in pre-Interstate garb.  I don't think this portion of 238 was ever Route 9.

- Route 57 between Glendora and the Kellogg Interchange is former I-210, before State Route 210 was established from Glendora east to Redlands.

- The freeway portion of US 101 in the Presidio east of Route 1 had been part of the proposed I-480, and the freeway portion of Route 1 in the Presidio had been part of the original I-280 proposals pre-1968.

- The Route 132 expressway being constructed now in Modesto was originally planned as I-5W.

- I-380 in San Bruno was originally proposed in the late sixties as Route 186.

- I-105 near LAX was originally legislatively part of State Route 42, though never signed as such as the parallel Firestone Boulevard route (pre-1959 Route 10) remained part of 42 even as 105 was being constructed.

- Portions of I-40 are former US 66, particularly right in Barstow at I-15.

I think the OP was referring specifically to instances where a highway was Interstate X, then renumbered Interstate Y.  The list of highways that were sub-interstate that are now interstate is as long as the list of interstates, and we can play that game forever.  Yes, it's interesting and I like it, but I think the topic was specifically renumbered interstates.

Your earlier example of I-20 in East Dallas becoming US 80 was kinda the template here but yeah I see where it is more about one interstate becoming another.

SM-G973U1

Think US 80 taking over I-20 and US 6 over I-84 are rare occurrences.  Even I-895 to NY 895 is not the same due to freeway downgrade there.

Yes, comparatively, the interstate highway system is young enough that decommissioning former interstate routes is very unusual.  I am fascinated with Business I-80 through Sacramento for this same reason.   Freeways are expensive to build, so re-routing another freeway or abandoning a freeway can be very costly. 

[TheStranger]

Yes, comparatively, the interstate highway system is young enough that decommissioning former interstate routes is very unusual.  I am fascinated with Business I-80 through Sacramento for this same reason.   Freeways are expensive to build, so re-routing another freeway or abandoning a freeway can be very costly. 

With Business I-80 in Sacramento, the only portions of it that were built as I-80 (as opposed to originally US 40 or US 99W/US 99E) are the Pioneer Bridge, WX Freeway, and part of the midtown north-south section between 29th/30th Streets.  The rest predated the Interstate system and is to some extent why CalTrans had hoped to build a new alignment along the railroad tracks in North Sacramento prior to the 1979 local vote that shifted funding for that to light rail.

There aren't that many freeways in California that are "former Interstate" and no longer in the system, beyond the following:

- Santa Ana Freeway/US 101 between I-5 and I-10, was I-105 for a couple of years in the 1960s but never signed.  the San Bernardino Freeway segment between US 101 and I-10 was I-110 but never signed, not sure if that counts as it is signed as I-10.

- Former US 395/I-15 through Miramar MCAS, bypassed by the current I-15.

- Former I-80 along the Central Freeway, not sure if ever fully signed on it though.  Partially US 101 and partially now essentially an unnumbered route to Octavia Boulevard.

- Business 80/US 50, depending on how one counts the unsigned I-305 segment.

- Would Route 99 being Temporary I-5 between Sacramento and Stockton in the 1970s count?

- Not sure if I-280 was ever signed on the portion of Route 1 between current I-280 in Daly City and Font Boulevard in SF.

[dvferyance]

Tennessee had I-181 renumbered to I-26 and I-265 renumbered to a rerouted I-65.

[Great Lakes Roads]

I can think of three for Indiana...

1. I-465 to I-865 (2002)- formerly called "The 465 dogleg".
2. I-294 (Borman Freeway from Tri-State to ITR) to I-94- was cosigned with 80 and 90. Deleted in 1965 after a reroute of I-94 off of the Toll Road and the Chicago Skyway and I-90 stayed on the tolled section towards Chicago to avoid confusion.
3. I-164 to I-69 (2014)- Completed in the '90s to connect Evansville with I-64. Resigned as I-69 in 2014 after a 60+ mile section opened to traffic in 2012.

[hobsini2]

Well the obvious ones in Illinois were where state or US highways became interstates.
I-88 Reagan Tollway was IL 5 E-W Tollway and before that was IL 190 and before that was US Toll 30.
I-290 Eisenhower Expy was at one point I-90 until 1978 when 90 got rerouted onto the Kennedy Expy and Northwest Tollway.
I-90 Addams (NW) Tollway was IL 194 until 1978.
I-190 was IL 594.
I-39 was added to US 51 and I-90.
I-72 was added to US 36 in the 1990s.
I-172 was IL 336 until the 1990s.

[ilpt4u]

I can think of three for Indiana...

1. I-465 to I-865 (2002)- formerly called "The 465 dogleg".
2. I-294 (Borman Freeway from Tri-State to ITR) to I-94- was cosigned with 80 and 90. Deleted in 1965 after a reroute of I-94 off of the Toll Road and the Chicago Skyway and I-90 stayed on the tolled section towards Chicago to avoid confusion.
3. I-164 to I-69 (2014)- Completed in the '90s to connect Evansville with I-64. Resigned as I-69 in 2014 after a 60+ mile section opened to traffic in 2012.

Well the obvious ones in Illinois were where state or US highways became interstates.
I-88 Reagan Tollway was IL 5 E-W Tollway and before that was IL 190 and before that was US Toll 30.
I-290 Eisenhower Expy was at one point I-90 until 1978 when 90 got rerouted onto the Kennedy Expy and Northwest Tollway.
I-90 Addams (NW) Tollway was IL 194 until 1978.
I-190 was IL 594.
I-39 was added to US 51 and I-90.
I-72 was added to US 36 in the 1990s.
I-172 was IL 336 until the 1990s.

Were not I-90 and I-94 swapped for the Skyway and Bishop Ford, at one point, and also in Indiana on the Indiana Toll Road and Borman?

[hobsini2]

I can think of three for Indiana...

1. I-465 to I-865 (2002)- formerly called "The 465 dogleg".
2. I-294 (Borman Freeway from Tri-State to ITR) to I-94- was cosigned with 80 and 90. Deleted in 1965 after a reroute of I-94 off of the Toll Road and the Chicago Skyway and I-90 stayed on the tolled section towards Chicago to avoid confusion.
3. I-164 to I-69 (2014)- Completed in the '90s to connect Evansville with I-64. Resigned as I-69 in 2014 after a 60+ mile section opened to traffic in 2012.

Well the obvious ones in Illinois were where state or US highways became interstates.
I-88 Reagan Tollway was IL 5 E-W Tollway and before that was IL 190 and before that was US Toll 30.
I-290 Eisenhower Expy was at one point I-90 until 1978 when 90 got rerouted onto the Kennedy Expy and Northwest Tollway.
I-90 Addams (NW) Tollway was IL 194 until 1978.
I-190 was IL 594.
I-39 was added to US 51 and I-90.
I-72 was added to US 36 in the 1990s.
I-172 was IL 336 until the 1990s.

Were not I-90 and I-94 swapped for the Skyway and Bishop Ford, at one point, and also in Indiana on the Indiana Toll Road and Borman?

I believe that was correct. I seem to recall having seen older maps from the late 50s that reflect that. I forgot about it.

[bassoon1986]

Tennessee had I-181 renumbered to I-26 and I-265 renumbered to a rerouted I-65.

Wasn't there also a portion of I-240 in Memphis that was I-255?


iPhone

[Scott5114]

There was a section of freeway in Oklahoma City that was originally numbered I-440, then was later renumbered as an I-240 extension, forming a 3/4 loop around the metro. Then, the north and west sides of I-240 became part of the I-44 extension to Wichita Falls, including the portion that was originally I-440.