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.
Interstate 90 in Washington
Interstate 90 is the longest freeway in Washington state, at nearly in length, and is the only Interstate to traverse the state from west to east across the Cascade Mountains. It is listed as part of the National Highway System, classifying important to the national economy, defense, and mobility, and the state's Highway of Statewide Significance program, recognizing its connection to major communities. A section of I-90 between Seattle and Thorp named the Mountains to Sound Greenway was designated in 1998 as a National Scenic Byway, in recognition of its scenic views.