Number of counties served by interstates

[mtantillo]

I had a random thought before. How many counties in the US are served by interstates? The answer for "number of counties containing interstates" was quickly calculated by ajfroggie using GIS and is 1,378.  But, if an interstate just "bumps" the corner of a county, with no interchange in the county, it doesn't really serve it? So....how many counties have an interstate running through it with no interchange? 

If you posted on the Freewayjim Facebook thread, feel free to re-post here.

[hbelkins]

Can't remember which county it is, but there's one in West Virginia along I-79 where just the corner of the county is nicked. It may be Gilmer County. It's between Flatwoods and Weston.

I-65 passes through Edmonson County, Ky., but there is no exit. The county is served by the interstate, however, via an exit in Warren County. Similarly, I-71 in Trimble County, but the US 421 exit in Henry County allows access to Trimble.

There are some answers to "Does Interstate X run through Y County?" on the mob-rule site.

There's a similar situation on the non-I-69 portion of the Western Kentucky Parkway. It clips the northern corner of Butler County without an interchange. And an "almost-but-not-quite" situation on the Mountain Parkway is being remedied. Currently, the only exit for the parkway in Clark County is its western terminus at I-64, so it is of no use to Clark County residents. A new exit for KY 974 in the eastern portion of the county is under construction and will open later this year.

[TCN7JM]

Interstate 80 in Iowa passes through one county (I think Madison) without an interchange. Interstate 29's coverage of Hamlin County, South Dakota, is questionable. I think its interchange with SD 22 is on the Deuel county line, so it should probably count.

[empirestate]

That's all well and good, but what about the opposite scenario, where a county is served by an interchange that is located in an adjacent county?

[agentsteel53]

Interstate 80 in Iowa passes through one county (I think Madison) without an interchange. Interstate 29's coverage of Hamlin County, South Dakota, is questionable. I think its interchange with SD 22 is on the Deuel county line, so it should probably count.

you can travel I-29 SB to SD-22 WB and stay entirely within Hamlin County, so it definitely counts.

[roadfro]

Interstate 80 in Iowa passes through one county (I think Madison) without an interchange.

Similarly, I-80 passes through Storey County between Washoe County (where Reno is) and Lyon County (where Fernley is) with no interchanges. However, this stretch in Storey County is less than a mile long--you can actually see the next county line sign as you past the first one entering Storey County.

[Scott5114]

In Oklahoma:

I-35 serves Love, Carter, Murray, Garvin, McClain, Cleveland, Oklahoma, Logan, Payne, Noble, and Kay counties, a total of 11 counties.
I-40 serves Beckham, Washita, Custer, Caddo, Canadian, Oklahoma, Pottawatomie, Seminole, Okfuskee, Okmulgee, McIntosh, Muskogee, and Sequoyah counties, a total of 13 counties. We can throw out Oklahoma since it's also served by I-35, dropping us to 12 counties.
I-44 serves Cotton, Comanche, Caddo, Grady, McClain, Cleveland, Oklahoma, Lincoln, Creek, Tulsa, Rogers, Mayes, Craig, and Ottawa counties, a total of 14 counties. We can throw out McClain, Cleveland, and Oklahoma since they're also served by I-35, and Caddo because it's also served by I-40, dropping us to 10 counties.*
We can disregard the 3dis because they all serve the same counties as their parents.

This gives us a total of 34 out of 77 counties (44%) served by Interstates in Oklahoma. Of these, Caddo County is the only county to have a stretch of Interstate with no interchanges, but this county is served by another county with interchanges.*

*There is a strange occurrence along I-44 that could be counted as a 35th county served by the interstate system. The flyover ramp from eastbound I-44 to the eastbound Will Rogers Turnpike, which carries EB I-44, appears to enter Wagoner County by a few hundred feet, although maps are generally too fuzzy to definitively state whether it does or not (the normally-definitive Control Section Map book shows it all in Rogers County, for example). From EB I-44, the only ramp heading south, definitively into Wagoner County, diverges from US-412 after I-44 does. Meanwhile, westbound I-44 doesn't enter Wagoner County at all, exiting from the mainline Will Rogers Turnpike far north of the county line (the mainline here is signed as a ramp to the Creek Turnpike). 

[Urban Prairie Schooner]

In Louisiana, an Interstate passes through these parishes:

Caddo, Bossier, Webster, Bienville, Lincoln, Ouachita, Richland, Madison, Desoto, Natchitoches, Rapides, Avoyelles, Evangeline, St. Landry, Calcasieu, Jefferson Davis, Acadia, Lafayette, St. Martin, Iberville, West Baton Rouge, East Baton Rouge, Ascension, St. James, St. John the Baptist, St. Charles, Jefferson, Orleans, St. Tammany, Tangipahoa, Livingston

which is 31 of the state's 64 parishes. (This does not include future I-49 south.) Of the list above, an interstate passes through, but does not have an interchange, within Evangeline Parish (I-49 nicks two corners). The same was true of St. James until the mid-1980s when the LA 641/Gramercy-Lutcher interchange was constructed, and of St. Charles until May 1993 when the north section of I-310 was opened.

[dgolub]

I-684 passes through Fairfield County, Connecticut, with no exit, but there are other interstates in Fairfield County.  I believe that the situation is similar with I-84 and Windham County, Connecticut.

[hbelkins]

That's all well and good, but what about the opposite scenario, where a county is served by an interchange that is located in an adjacent county?

That would increase the number of counties considered "served" by a significant percentage.

For example, Exit 41 on I-75 is for KY 80, London-Somerset. The exit is located in London (Laurel County) but Somerset is in adjacent Pulaski County. So is Pulaski County "served" by I-75?

What about Bourbon County, Ky.? Neither I-75 nor I-64 enter it, but there are multiple exits for Paris (the county seat) on the interstates. I-75's Exit 125 (northbound only) for US 460 and Exit 126 southbound for US 62/To US 460 list Paris, as does Exit 113 (US 27/68) on the 75/64 concurrency. In addition, westbound I-64's Exit 110 at Mt. Sterling, US 460/KY 11, uses Paris (eastbound uses Flemingsburg).

[Brandon]

Illinois:

I-24: 2
I-39: 7
I-55: 11
I-57: 19 (passes through Shelby and Clay w/o interchanges)
I-64: 6
I-70: 7
I-72: 7
I-74: 11
I-80: 8 (all lanes do actually clip Kendall with the north half of Exit 122 in Kendall)
I-88: 8
I-90: 4 (passes through McHenry w/o interchanges)
I-94: 2
I-155: 2
I-255: 3
I-355: 3
I-270: 1
I-172: 1 (meets I-72 in Pike - no other interchanges)
I-474: 2
I-180: 2
I-280: 2
I-190: 1
I-290: 2
I-294: 2 (Lake-Cook Rd interchange is solidly on I-294)

Of these that interstates pass through, three counties (Clay, McHenry, and Shelby) have no interchanges (2.94%).

There are a total of 63 counties in Illinois served by interstates for a total of 61.76% (63/102).

Some counties have more than one interstate, 27.45% (28/102).  Of these, only 21.57% (22/102) have interstate-to-interstate interchanges.  Some just have two interstates go through w/o meeting each other (Lee, Grundy, Woodford, Piatt, Fayette, and Cumberland).

[mapman1071]

Arizona

I-8 Yuma, Maricopa, Pinal
I-10 La Paz, Maricopa, Pinal, Pima, Cochise
(I-11 Pima, Pinal, Maricopa, Yavapai, Mohave)
I-15 Mohave
I-17 Maricopa, Yavapai, Coconino
I-19 Santa Cruz, Pima
I-40 Mohave, Yavapai, Coconino, Navajo, Apache

12/15 Counties Served 75%
No Interstates in Gila, Graham  or Greenlee Counties

[KEK Inc.]

Washington (17)

I-5:  Whatcom, Skagit, Snohomish, King, Pierce, Thurston, Lewis, Cowlitz, Clark (9)
I-90: King, Kittitas, Grant, Adams, Lincoln, Spokane (6)
I-82: Kittitas, Yakima, Benton (3)

I-205: Clark (1)
I-405: King, Snohomish (2)
I-705: Pierce (1)

I-182: Benton, Franklin (2)

All Interstates have interchanges in respective county.

Oregon (18)

I-5: Multnomah, Washington, Clackamas, Marion, Linn, Lane, Douglas, Josephine, Jackson (9)
I-82: Umatilla (1)
I-84: Multnomah, Hood River, Wasco, Sherman, Gilliam, Morrow, Umatilla, Union, Baker, Malheur (10)

I-105: Lane (1)
I-205: Multnomah, Clackamas (2)
I-405: Multnomah (1)

All Interstates have interchanges in respective county.

California (26)

I-5: Siskiyou, Shasta, Tehama, Gienn, Colusa, Yolo, Sacramento, San Joaquin, Stainislaus, Merced, Fresno, Kings, Kern, Los Angeles, Orange, San Diego (16)
I-8: San Diego, Imperial (2)
I-10: Los Angeles, San Bernardino, Riverside (3)
I-15: San Diego, Riverside, San Bernardino (3)
I-40: San Bernardino (1)
I-80: San Francisco, Almeda, Contra Costa, Solano, Yolo, Sacramento, Placer, Nevada (8)

I-105: Los Angeles (1)
I-205: San Joaquin, Alameda (2) (Terminus in Alameda; no interchange to local roads)
I-305 (Bus I-80): Sacramento (1)
I-405: Los Angeles, Orange (2)
I-505: Solano, Yolo (2)
I-605: Los Angeles (1)
I-805: San Diego (1)

I-110: Los Angeles (1)
I-210: Los Angeles, San Bernardino (2)
I-710: Los Angeles (1)

I-215: San Bernardino, Riverside (2)

I-280: San Francisco, San Mateo, Santa Clara (3)
I-380: San Mateo (1)
I-580: Marin, Contra Costa, Alameda, San Joaquin (4)
I-680: Solano, Contra Costa, Alameda, Santa Clara (4)
I-780: Solano (1)
I-880: Alameda, Santa Clara (2)
I-980: Alameda (1)


The West Coast rarely has "bumps" or grazes with Interstates in county lines.  The only one that might be applicable is I-205/I-580 near Tracy.

[Duke87]

So here's a question: what state has the highest percentage of its counties served by an interstate?

Connecticut has 7/8, or 87.5%. Can any other state beat that?
New Jersey has 18/21, or 85.7%. Close but no cigar.

And the obvious antithesis: what state has the lowest percentage of its counties served by an interstate? I'm guessing it'd have to be Hawaii, with 1/5, or 20.0%. Delaware has 1/3, or 33.3%, which is also pretty low.

[agentsteel53]

when I think of the American accent, I think of one that doesn't seem to exist anymore... the 1940s Hollywood newsreel announcer.  where did all those announcers go?

[jp the roadgeek]

I-684 passes through Fairfield County, Connecticut, with no exit, but there are other interstates in Fairfield County.  I believe that the situation is similar with I-84 and Windham County, Connecticut.

True with I-684.  Not true with I-84 in Windham County.  Exit 72 (CT 89) is in Ashford, which is Windham County.  Now, Litchfield County doesn't have a single interstate running through it.

[oscar]

And the obvious antithesis: what state has the lowest percentage of its counties served by an interstate? I'm guessing it'd have to be Hawaii, with 1/5, or 20.0%. Delaware has 1/3, or 33.3%, which is also pretty low.

Nebraska:  16/93, or 17.2%.

[agentsteel53]

Nebraska:  16/93, or 17.2%.

that's what happens when the main north-south is on the other side of the river.

I'll bet North Dakota and South Dakota have a higher proportion. 

[Laura]

13/24 counties in MD are served by an interstate, and all of them have exits in their counties. This number includes Baltimore City. Carroll county barely has an interchange - I-70 at MD 27 - part of the interchange is in Frederick county.


iPhone

[TCN7JM]

Nebraska:  16/93, or 17.2%.

that's what happens when the main north-south is on the other side of the river.

I'll bet North Dakota and South Dakota have a higher proportion.

You'd be correct, by my count:

North Dakota: 14/53, 26.4%

South Dakota: 21/66, 31.8%

Of course Nebraska's counties are also tiny compared to North Dakota's (which is why two main Interstates in ND run through less counties than NE with one).
Edit: Add missing comma because my OCD was going off.

[agentsteel53]

I never thought of NE counties as being tiny, since they have that behemoth in the northwest... but yes, looking at a map, I see many small ones.

[WNYroadgeek]

That's all well and good, but what about the opposite scenario, where a county is served by an interchange that is located in an adjacent county?

Let's see, then...

I-86/NY 17 Exits 46 (Steuben County) and 52 (Chemung County) are both signed for Watkins Glen (Schuyler County).

I-86/NY 17 Exits 54 (Chemung County) and 63 (Tioga County) are both signed for Ithaca  (Tompkins County). I-81 Exit 11 (Cortland County) is also signed for Ithaca.

Thruway Exits 41 (Seneca County), 42, and 43 (both Ontario County) are all signed for towns in Wayne County (Clyde, Lyons, and Palmyra, respectively)..

Thruway Exit 48A (Genesee County) is signed for Medina (Orleans County).

[Scott5114]

when I think of the American accent, I think of one that doesn't seem to exist anymore... the 1940s Hollywood newsreel announcer.  where did all those announcers go?

non-sequitur post is non-sequitur!

but to answer your question, that accent is called a "Transatlantic" accent, an attempt to manufacture an accent between a New York and a British accent. Eventually, news stations stopped bothering to attempt this, and the Iowa accent became the "standard" news accent.

[Molandfreak]

when I think of the American accent, I think of one that doesn't seem to exist anymore... the 1940s Hollywood newsreel announcer.  where did all those announcers go?

non-sequitur post is non-sequitur!

but to answer your question, that accent is called a "Transatlantic" accent, an attempt to manufacture an accent between a New York and a British accent. Eventually, news stations stopped bothering to attempt this, and the Iowa accent became the "standard" news accent.

So no one "naturally" had this accent?

This post actually belongs here.

[sammi]

when I think of the American accent, I think of one that doesn't seem to exist anymore... the 1940s Hollywood newsreel announcer.  where did all those announcers go?

non-sequitur post is non-sequitur!

but to answer your question, that accent is called a "Transatlantic" accent, an attempt to manufacture an accent between a New York and a British accent. Eventually, news stations stopped bothering to attempt this, and the Iowa accent became the "standard" news accent.

So no one "naturally" had this accent?

This post actually belongs here.

I think he misplaced the post.