List of suffixed Interstate Highways
|Dwight D. Eisenhower National System of Interstate and Defense Highways|
The 1958 Interstate Highway System plan included many suffixed Interstates.
|Formed:||June 29, 1956|
|Interstates:||Interstate X (I-X)|
Currently the Interstate Highway System includes seven suffixed routes that are signed: 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; and Interstate 69C, Interstate 69E and Interstate 69W in South Texas; in addition, Interstate 480N in Ohio exists and is designated as such on mile markers and exit/entrance ramp signs, 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. Interstate 15E has since become Interstate 215, but both I-35E/I-35W and I-69 splits still exist.
List of suffixed Interstates
|Hillsboro, Texas (I-35) to Denton, Texas (I-35)|
|Burnsville, Minnesota (I-35) to Forest Lake, Minnesota (I-35)|
|Mexican border to Victoria, Texas (I-69/US 59)|
|25px I-480N||Warrensville Heights, Ohio (I-480 to I-271) via North Randall, Ohio; unsigned|
|Tracy, California (I-5) to Dunnigan, California (I-5)||In the 1958 plan; I-5E changed to I-5 and I-5W to I-580, I-80 and I-505 in 1964|
|25px I-15E||Temecula, California (I-15) to Devore, California (I-15)||Renumbered from I-215 in 1973 and back to I-215 in 1982|
|25px I-15W||Pocatello, Idaho (I-15) to Rupert, Idaho (I-80N)||In the 1958 plan; became I-86 in 1980|
|25px I-24W||Jackson, Tennessee (I-40) to Hayti, Missouri (I-55)||Did not connect to I-24; renumbered I-155 in 1964|
|25px I-35W||Wichita, Kansas (I-35) to Salina, Kansas (I-70)||In the 1958 plan; renumbered I-135 in 1976|
|25px I-59B||Bypass for I-59 around Birmingham, Alabama||Renumbered I-459|
|25px I-70S||Washington, Pennsylvania (I-70) to New Stanton, Pennsylvania (I-70/I-80S)||In the 1958 plan; became part of I-70 and former I-70 became parts of I-79 and I-76 in 1964|
|Frederick, Maryland (I-70) to Washington, DC (I-66/I-95) and Baltimore, Maryland (I-83/I-95)||In the 1958 plan; became I-270 and I-70 in 1973|
|25px I-75E||Bypass for I-75 around Tampa-St. Petersburg, Florida||Renumbered I-275 in 1973, and swapped with I-75 in 1980|
|25px I-80N||Echo, Utah (I-80) to Portland, Oregon (I-5)||In the 1958 plan; became I-84 in 1980|
|25px I-180N||Spur from I-80N to Boise, Idaho||This was the only suffixed three-digit Interstate; all other spurs of suffixed routes had no suffix; became I-184 in 1980|
|25px I-80S||Big Springs, Nebraska (I-80) to Denver, Colorado (I-25/I-70)||In the 1958 plan; became I-76 in 1980|
|25px I-80N||Neola, Iowa (I-80) to Loveland, Iowa (I-29)||Became part of I-680 in 1973|
|25px I-80N||Norwalk, Ohio (I-80/I-90) to Edinburg, Ohio (I-80)||In the 1958 plan; became part of I-80 by 1962|
|25px I-80S||Youngstown, Ohio (I-80) to Camden, New Jersey (I-295)||Extended west to Lodi, Ohio by 1962 over former I-80; east end truncated to Monroeville, Pennsylvania and the part east of Monroeville renumbered I-76 in 1964; the rest became part of I-76 in 1970|
|25px I-81E||Scranton, Pennsylvania (I-81) to Scotrun, Pennsylvania (I-80)||In the 1958 plan; became I-380 ca. 1973|
- 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.
- "1970s". Kansas Celebrates 50 Years of Interstates. Kansas Department of Transportation. Retrieved 2013-07-16.