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 16 in South Dakota
US 16 is also known as Mount Rushmore Road in western South Dakota. The highway enters South Dakota east of Newcastle, Wyoming. It travels near Jewel Cave, the third-longest cave in the world. The highway goes through the city of Custer and shares alignment with US 385. East of Hill City, US 16 splits off US 385. It then becomes a four-lane divided highway, with the two roadways separated by up to in some places, including the old gold-mining town of Rockerville, South Dakota, which is contained entirely in the median of US 16. In Rapid City, US 16 follows Mount Rushmore Road to a concurrency with SD 44 (Omaha Street) to the southern terminus of I-190. US 16 stays concurrent with I-190 until both highways end at I-90.