List of Interstate Highways in Utah
The Interstate Highways in Utah are maintained by the Utah Department of Transportation (UDOT). The Interstate Highway System is a nationwide system with only a small portion of these routes entering Utah. Originally, the State Road Commission of Utah, created on March 23, 1909 was responsible for maintenance, but these duties were rolled into the new UDOT in 1975. There are of Interstates within the state. The longest is Interstate 15 (I-15) at and the shortest is I-215 at . One unique former route is Interstate 415, which was never signed as such, and was only used as a temporary designation for the eastern portion of what is now the Interstate 215 belt loop around Salt Lake City.
U.S. Route 6
U.S. Route 6 (US 6), also called the Grand Army of the Republic Highway, honoring the American Civil War veterans association, is a main route of the U.S. Highway system. While it currently runs east-northeast from Bishop, California to Provincetown, Massachusetts, the route has been modified several times. The highway's longest-lasting routing, from 1936 to 1964, had its western terminus at Long Beach, California. During this time, US 6 was the longest highway in the country.