Longest Stretches of Interstates You've Still Not Traveled

[Big John]

I-90 from Cle Elum, WA to Tomah, WI.

[catch22]

I-10 from its intersection with I-75 in Florida all the way to its western terminus.

[Rothman]

Forgot to update I-5 from my San Diego trip some months ago...

I-44, MO 133 to Southern Terminus: 498 miles
I-29, Canadian Border to County 10, Elk Point, SD: 452 miles
I-5, I-205 to CA 76: 404 miles
I-10, east side of downtown rectangle in Phoenix to I-25: 388 miles
I-5, OR 99 to CA 120: 377 miles
I-25, I-90 to CO 7: 370 miles
I-25, US 50 to I-40, 334 miles
I-90, US 93 to WA 17, 288 miles
I-10, TX 17 to TX 41, 278 miles
I-49, I-435 to I-40, 268 miles
I-15, I-90 to Canadian Border, 267 miles
I-55, I-270 to I-40, 262 miles

[TheHighwayMan3561]

I-95 south of Teaneck (have physically seen it from FL Turnpike, though)
I-5 from LA to Portland
I-15 from SLC to Butte
no meaningful independent sections of I-70 east of St. Louis, or I-64 for that matter
I-45

[Rothman]

Dear me, dear me, dear me...the I-55 one I mentioned last in my list is one I've chopped up as well.  Remaining longest segment is too small to list: 130 miles (I-270 to US 62 north of Sikeston).

I-44, MO 133 to Southern Terminus: 498 miles
I-29, Canadian Border to County 10, Elk Point, SD: 452 miles
I-5, I-205 to CA 76: 404 miles
I-10, east side of downtown rectangle in Phoenix to I-25: 388 miles
I-5, OR 99 to CA 120: 377 miles
I-25, I-90 to CO 7: 370 miles
I-25, US 50 to I-40, 334 miles
I-90, US 93 to WA 17, 288 miles
I-10, TX 17 to TX 41, 278 miles
I-49, I-435 to I-40, 268 miles
I-15, I-90 to Canadian Border, 267 miles

[Ted$8roadFan]

Most interstates outside of New England.

[7/8]

My top 3:
1) I-35: From East Rundberg Lane, Austin, TX to I-80 in West Des Moines, IA (approx. 1464 km / 910 mi)
2) I-70: From Pena Blvd in Denver, CO to US 54 in Kingdom City, MO (approx. 1184 km / 736 mi)
3) I-80: From I-84 in Echo, UT to I-76 in Big Springs, NE (approx. 859 km / 534 mi)

[Rothman]

Eh, we'll add I-8, too...

I-44, MO 133 to Southern Terminus: 498 miles
I-29, Canadian Border to County 10, Elk Point, SD: 452 miles
I-5, I-205 to CA 76: 404 miles
I-10, east side of downtown rectangle in Phoenix to I-25: 388 miles
I-5, OR 99 to CA 120: 377 miles
I-25, I-90 to CO 7: 370 miles
I-25, US 50 to I-40, 334 miles
I-90, US 93 to WA 17, 288 miles
I-10, TX 17 to TX 41, 278 miles
I-49, I-435 to I-40, 268 miles
I-15, I-90 to Canadian Border, 267 miles
I-8, Exit 89, Ocotillo to I-10, 265 miles

[Rothman]

Sacramento meet allowed a lot of I-5 clinching...

I-44, MO 133 to Southern Terminus: 498 miles
I-29, Canadian Border to County 10, Elk Point, SD: 452 miles
I-10, east side of downtown rectangle in Phoenix to I-25: 388 miles
I-25, I-90 to CO 7: 370 miles
I-25, US 50 to I-40, 334 miles
I-90, US 93 to WA 17, 288 miles
I-10, TX 17 to TX 41, 278 miles
I-5, OR 99 to Grimes Arbuckle Road: 271 miles
I-49, I-435 to I-40, 268 miles
I-15, I-90 to Canadian Border, 267 miles
I-8, Exit 89, Ocotillo to I-10, 265 miles
I-5: I-405, northern interchange to CA-76, 104 miles

[jlam]

Mine has to be I-90 east of South Dakota exit 57. ~ 1,893 miles.

Oop, I forgot to update this after a visit to the booming metropolis of Vivian, SD. Down to 1,738 miles.

[roadman65]

Interstate 10 between the LA Metro and San Antonio.

Alot of I-80 and I-90.

I-55 in Mississippi and Illinois.

[ran4sh]

I-90 from Madison to eastern Washington

I-80 from Walcott (Quad Cities area) to Sacramento

I-94 from Madison west

I-70 from Columbia MO west

I-25 whole length

I-35 whole non-overlap length

I-15 from Las Vegas north

[NWI_Irish96]

Forgot to update this back in September.

I-10 Tucson, AZ, to LaPlace, LASealy, TX: 13811012 miles
I-80 San Francisco to Salt Lake City: 731 miles
I-90 Seattle to Livingston, MT: 700 miles
I-5 Stockton, CA, to Longview, WA: 670 miles
I-15 Brigham City, UT, to northern end: 630 miles
I-29 Council Bluffs, IA, to northern end: 570 miles
I-20 Fort Worth, TX, to Meridian, MS: 512 miles

[JayhawkCO]

Didn't update this from previous trips. All my stretches more than 250 miles:

I-5 from Oceanside, CA to I-205 outside of Portland - 1,033 Miles
I-5 from Oceanside, CA to Exit 31 in Medford, OR - 773 miles
I-75 from I-70 near Dayton to the Canadian Border - 519 miles
I-10 from the end in Santa Monica to I-17 in Phoenix - 386 miles
I-10 from I-20 near Big Spring to I-35 in San Antonio - 383 miles
I-85 from I-75 in Atlanta to NC157 in Durham, NC - 375 miles
I-A1 from I-A3 in Palmer to the Canadian Border - 371 miles
I-8 from Lake Jennings Park Road in Lakeside, CA to I-10 near Casa Grande - 326 miles
I-40 from the first exit away from I-15 in Barstow to Williams, AZ - 316 miles
I-15 from I-90 in Butte to the Canadian Border - 266 miles Got this shortened under 250 miles by visiting Helena

[Rothman]

Just took a decent chunk off of I-44.  Took a big chunk from SD to Canadian Border off, too (just going to remove that one from my list).

That leaves:

I-10, east side of downtown rectangle in Phoenix to I-25: 388 miles
I-25, I-90 to CO 7: 370 miles
I-25, US 50 to I-40, 334 miles
I-90, US 93 to WA 17, 288 miles
I-10, TX 17 to TX 41, 278 miles
I-5, OR 99 to Grimes Arbuckle Road: 271 miles
I-49, I-435 to I-40, 268 miles
I-15, I-90 to Canadian Border, 267 miles
I-8, Exit 89, Ocotillo to I-10, 265 miles
I-44, OK 4 to southern terminus, 114 miles
I-5: I-405, northern interchange to CA-76, 104 miles

[Konza]

Spent some time on Travel Mapping researching this, and was a little surprised at what I found.

The top fifteen:

372 miles:  I-85 from US 29/I-185 to I-95 (SC-NC-VA)
367 miles:  I-90 from I-82 to US 93 (WA-ID-MT)
269 miles:  I-15 from I-90 to the Canadian border (MT)
264 miles:  I-95 from I-295 (exit 44) to the Canadian border (ME)
247 miles:  I-15 from I-86 to I-90 (ID-MT)
245 miles:  I-86 from I-90 to I-81 (PA-NY)
230 miles:  I-77 from I-26 to I-81 (SC-NC-VA)
227 miles:  I-40 from I-240 (exit 52) to I-885 (exit 279) (NC)
226 miles:  I-90 from US 75 to US 52 (MN)
174 miles:  I-87 from I-90 to US 11 (NY)
174 miles:  I-84 from I-205 to I-82 (OR)
172 miles:  I-75 from M-59 to US 127 (MI)
170 miles:  I-81 from I-88 to the Canadian border (NY)
167 miles:  I-77 from I-64 to US 250 (WV-OH)
161 miles:  I-90 from I-25 to I-190 (exit 57) (WY-SD)

Some notes:  I-86 (NY-PA) is the longest Interstate route I have not traveled.

I've traveled very little of I-87 but have traveled the concurrency with I-90 in the Albany area, which pretty much splits the route in half.

[formulanone]

843 miles of I-90 from Post Falls, ID to Spearfish, SD.

686 miles of I-15 from Salt Lake City to the Canadian border.

640 miles of I-40 from (west of) Albuquerque to Barstow, CA.

625 miles of I-80 from Roseland, CA to Salt Lake.