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 2
By the time the U.S. Highway system was finalized in late 1926, one relatively minor change had been made to US 2; it was swapped with US 1 between Bangor and Houlton, Maine, placing US 2 along the entire portion of Route 15 east of St. Johnsbury. Several other major parts of the auto trail received numbers, most notably US 30 from Portland, Oregon east to Pendleton, US 195 in eastern Washington, and US 23 in Michigan's Lower Peninsula. In the mid-1930s, much of New York's portion of the road became US 104, and the part southeast of Littleton, New Hampshire to Portland, Maine became US 302, but by far the longest piece was that followed by US 2 between St. Ignace and Bonners Ferry. In 1946, US 2 was extended west of its original western terminus in Bonners Ferry in Idaho to Everett in Washington via Spokane along what was then Alternate US 10.