List of suffixed Interstate Highways
In the United States, there are currently seven "suffixed" Interstate Highways. In addition to the Interstate 35 split into Interstate 35E and Interstate 35W at Dallas-Fort Worth, Texas, a similar split into Interstate 35E and Interstate 35W at Minneapolis–St. Paul, Minnesota, exists, as well as Interstate 69C, Interstate 69E and Interstate 69W in South Texas. Interstate 480N in Ohio exists and is designated as such on mile markers but is otherwise unsigned. However, there were once many more, as the three-digit Interstates were not designated until after all major routes were assigned numbers, including some short connections and spurs. (A few of the shortest, including I-190 and I-195, were assigned three-digit numbers almost immediately.) Most were not equal splits like on I-35, but had the main route continue through, and often the suffixed route never returned to its parent. In 1980, AASHTO abolished the majority of suffixes due to confusion, renumbering them as three-digit Interstates, but several that return to their parents were kept. For example, Interstate 15E has since become Interstate 215, but both I-35E/I-35W and I-69 splits still exist, the I-69 splits being recently designated.
|Dwight D. Eisenhower National System of Interstate and Defense Highways|
Highway shields for Interstate 35E and Interstate 69C
The 1958 Interstate Highway System plan included many suffixed Interstates.
|Formed||June 29, 1956|
|Interstates||Interstate X (I-X)|
|Number||Length (mi)||Length (km)||Southern or western terminus||Northern or eastern terminus||Formed||Removed||Notes|
|I-5W||—||—||I-5 in Tracy, CA||I-5 in Dunnigan, CA||—||—||Replaced by I-580, I-80 and I-505|
|I-5E||—||—||I-5 in Tracy, CA||I-5 in Dunnigan, CA||1958||1982||Replaced by I-5|
|I-15E||—||—||I-15 in Temecula, CA||I-15 in Devore, CA||1973||1982||Renumbered from I-215 in 1973 and back to I-215 in 1982|
|I-15W||—||—||I-15 in Murrieta, CA||I-15 in San Bernardino, CA||1957||—||Became I-15 in 1957|
|I-15W||—||—||I-80N in Rupert, ID||I-15 in Pocatello, ID||1958||1980||Became I-86 in 1980; was also planned as I-82N|
|I‑24W||—||—||I-55 in Hayti, MO||I-40 in Jackson, TN||—||1964||Did not connect to I-24; renumbered I-155|
|I-35W||85.20||137.12||I-35 in Hillsboro, TX||I-35 in Denton, TX||1959||current|
|I-35E||96.76||155.72||I-35 in Hillsboro, TX||I-35 in Denton, TX||1959||current|
|I-35W||—||—||I-35 in Wichita, KS||I-70 in Salina, Kansas||—||1976||Renumbered I-135|
|I-35W||41.78||67.24||I-35 in Burnsville, MN||I-35 in Forest Lake, MN||—||—|
|I-35E||39.34||63.31||I-35 in Burnsville, MN||I-35 in Forest Lake, MN||—||—|
|I-59B||—||—||Bypass for I-59 around Birmingham, AL||—||—||Renumbered I-459|
|I-69W||1.43||2.30||Fed. 85D at Mexican border on World Trade International Bridge at Laredo, TX||I-35/US 83/US 59/Loop 20 in Laredo, TX||2014||current|
|I-69C||18.02||29.00||I-2/US 83/US 281 in Pharr, TX||US 281/Bus. US 281 near Edinburg, TX||2013||current|
|I-69E||53.31||85.79||East Rio Grande Valley segment: US 77/US 83/University Boulevard in Brownsville, TX
Corpus Christi area segment: US 77/SH 44 in Robstown, TX
|East Rio Grande Valley segment: US 77/Bus. US 77 near Raymondville, TX
Corpus Christi area segment: I-37/US 77 in Corpus Christi, TX
|I-70S||—||—||I-70 in Washington, PA||I-70/I-80S in New Stanton, PA||1958||1964||Became part of I-70 and former I-70 became parts of I-79 and I-76|
|I-70N||—||—||I-70 in Frederick, MD||I-83/I-95 in Baltimore, MD||1958||1973||Became I-70|
|I-70S||—||—||I-70 in Frederick, MD||I-66/I-95 in Washington, DC||1958||1973||Became I-270|
|I-75E||—||—||Bypass for I-75 around Tampa-St. Petersburg, FL||—||1973||Renumbered I-275; later swapped with I-75 in 1980|
|I‑80N||—||—||I-5 in Portland, OR||I-80 in Echo, UT||1958||1980||Became I-84|
|I‑80S||—||—||I-25/I-70 in Denver, CO||I-80 in Big Springs, NE||1958||1980||Became I-76|
|I-80N||—||—||I-80 in Neola, IA||I-29 in Loveland, IA||—||1973||Became part of I-680|
|I-80N||—||—||I-80/I-90 in Lorain County, OH||I-80S/SR 5 in Braceville Township, OH||1960||1962||Redesignated as I-80|
|I‑80S||—||—||I-80 in Youngstown, OH||I-295 in Camden, NJ||—||1970||Extended west to Lodi, OH, by 1962 over former I-80; east end truncated to Monroeville, PA, and the part east of Monroeville renumbered I-76 in 1964; the rest became part of I-76|
|I-81S||—||—||I-81 in Scranton, PA||I-80 in Crescent Lake, PA||—||1964||Formerly I-82, became I-81E (now I-380)|
|I-81E||—||—||I-81 in Scranton, PA||I-80 in Scotrun, PA||1964||1973||Formerly I-81S, became I-380|
|I‑82S||—||—||Burley, ID||Tremonton, UT||1957||—||Became I-84|
|I-82N||—||—||Burley, ID||Pocatello, ID||1957||—||Became I-86|
|I-90N||—||—||Buffalo, NY||Canadian border at Lewiston, NY||1957||1959||Original designation for I-190 in New York, renamed I-190|
|I-94N||—||—||Muskegon, MI||I-94 in Grand Rapids, MI||1957||1959||Became I-196 in 1959 and then I-96 in 1964|
|I-180N||—||—||I-80N||Boise, ID||—||1980||This was the only suffixed three-digit Interstate (until I-480N in Ohio was designated); all other spurs of suffixed routes had no suffix; became I-184|
|I-480N||1.99||3.20||I-480 in Maple Heights, OH||US 422 in Warrensville Heights, OH||1974||current||Signed as I-480 on guide signs and reassurance markers, signed as I-480N on mile markers|
|I-495X||1.50||2.41||I-495 in Bethesda, MD||Clara Barton Parkway in Cabin John, MD||1965||current||Also known as Cabin John Parkway; designated internally by MDSHA as I-495X; unsigned; trucks are not allowed on the length of the freeway|
- Weingroff, Richard F. (Summer 1996). "Federal-Aid Highway Act of 1956, Creating the Interstate System". Public Roads. Washington, DC: Federal Highway Administration. 60 (1). Retrieved March 16, 2012.
- Kansas Department of Transportation (2009). "1970s". Kansas Celebrates 50 Years of Interstates. Kansas Department of Transportation. Archived from the original on February 12, 2012. Retrieved July 16, 2013.
- "Spring to Bring Debut for Interstate Road Numbering". The Herald-Press. St. Joseph, Michigan. Associated Press. January 8, 1959. p. 5. OCLC 10117184.
- "Route Number Changes Slated". Lansing State Journal. December 12, 1963. p. 10. OCLC 61312043. Retrieved September 17, 2017 – via Newspapers.com.
- Office of Technical Services (January 1999). "Technical Services Straight Line Diagram for I-480N" (PDF). Ohio Department of Transportation.
- Highway Information Services Division (December 2013). "Highway Location Reference" (Webpage). Maryland Department of Transportation.
- Kirby, J.P.; et al. "Frequently Asked Questions - What are/where all the suffixed Interstates?". misc.transport.road.