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.
Appalachia
The effort to connect Appalachia with the outside world has required numerous civil engineering feats. Millions of tons of rock were removed to build road segments such as Interstate 40 through the Pigeon River Gorge at the Tennessee-North Carolina state line and U.S. Route 23 in Letcher County, Kentucky. Large tunnels were built through mountain slopes at Cumberland Gap to speed up travel along U.S. Route 25E. The New River Gorge Bridge in West Virginia, completed in 1977, was the longest and is now the fourth-longest single-arch bridge in the world. The Blue Ridge Parkway's Linn Cove Viaduct, the construction of which required the assembly of 153 pre-cast segments up the slopes of Grandfather Mountain, has been designated a historic civil engineering landmark.