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|Dwight D. Eisenhower National System of Interstate and Defense Highways
Intrastate Interstate Highways in the 48 contiguous states highlighted in red
||June 29, 1956
||Interstate X (I-X)
There are several intrastate Interstate Highways; that is, Interstate Highways that are located entirely within one state. The concept is somewhat contradictory; the word "Interstate" refers to the way the entire group of highways is funded (as a national system of interconnected highways), not to the route each given highway travels.
Within the contiguous 48 states 
This list includes only primary Interstate highways (those with route numbers less than 100). Most (but not all) three digit Interstates are intrastate. Among the three digit interstates, examples of non-intrastate routes include I-435 in Kansas City, Missouri and Kansas City, Kansas and I-535 which crosses from Duluth into Superior.
Additionally, there are six Interstate highways that are almost entirely intrastate:
- Interstate 57 is located almost entirely in Illinois, but it has a relatively short section in Missouri, compared to its long journey through the "Land of Lincoln". I-57 is 386 miles (621 km) in length, with twenty-two miles (35 km) found within Missouri.
- Interstate 66 is located almost entirely in Virginia, but it has a quite short section in the District of Columbia. I-66 is 75 miles (121 km) in length, with one-half mile (0.8 km) in D.C.
- Interstate 72 is located almost entirely in Illinois, but it has a very short section in Missouri. I-72 is 184 miles (296 km) in length, with two miles (3.2 km) in Missouri.
- Interstate 76 (western section) is located almost entirely in Colorado, but it has a very short section in Nebraska that connects Interstate 80. I-76 is 186 miles (299 km) in length, with less than three miles (4.8 km) in Nebraska.
- Interstate 82 is located almost entirely in Washington, but it has a short section in Oregon that connects to Interstate 84. I-82 is 144 miles (232 km) in length, with just about eleven miles (18 km) in Oregon.
- Interstate 86 (eastern section) is located almost entirely in New York, but it has a short section in Pennsylvania that connects to Interstate 90. I-86 is 177 miles (285 km) in length (in the process of being expanded to 380 mi or 610 km), with less than seven miles (11 km) in Pennsylvania.
Outside of the contiguous 48 states 
As Alaska and Hawaii do not share land borders with any other U.S. state, their Interstate highways are all located fully within their respective state's boundaries. Puerto Rico is not a state; however, it also has highways funded by the Federal Government as Interstate highways.
Signed Interstates 
H-1, H-2, and H-3 stand for Hawaii-1, Hawaii-2, and Hawaii-3, respectively. These freeways are part of the Interstate Highway System and are thus called Interstate highways. These are all located on the heavily-populated island of Oahu, and there are none on the other islands.
Unsigned Interstates 
Interstate highways in Alaska and Puerto Rico are not signed as Interstate highways, and are designated as such primarily for purposes of Federal funding. Interstates A-1 through A-4 are located in Alaska, and Interstates PRI-1 through PRI-3 are located in Puerto Rico. These highways are not required to meet interstate standards, and as a result, most portions of these interstate highways are not grade-separate freeways. Freeways in Puerto Rico are primarily toll roads that are not funded through the Eisenhower Interstate System. Very few freeways exist in Alaska; they are located primarily near Anchorage, Fairbanks, and Wasilla.
- ^ 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.
- ^ a b c DeSimone, Tony (January 19, 2012). "Table 1: Main Routes of the Dwight D. Eisenhower National System Of Interstate and Defense Highways as of October 31, 2002". Route Log and Finder List. Federal Highway Administration. Retrieved March 28, 2012.
- ^ Obenberger, Jon; DeSimone, Tony (March 14, 2012). "Dwight D. Eisenhower National System of Interstate and Defense Highways: Interstate System Facts". Federal Highway Administration. Retrieved March 28, 2012.