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.
Washington State Route 20
Although US 12 has a larger east–west extent, SR 20 is the longest highway in Washington at , only longer than US 12. The highway has been called "The Most Beautiful Mountain Highway in the State of Washington."
SR 20 begins at a wye junction with US 101 at the southwest end of Discovery Bay on the Olympic Peninsula, just north of the terminus of SR 104. The highway travels northerly through the rural Quimper Peninsula and follows the east shore of Discovery Bay before reaching a junction with SR 19 near Jefferson County International Airport. SR 20 turns north onto the highway and passes Fort Townsend State Park on the southern outskirts of Port Townsend near Glen Cove. Within Port Townsend, the highway travels east through suburban areas as Sims Way and towards the historic downtown as Water Street. To the southwest of Port Townsend's historic district, the route turns southeast into the city ferry terminal. SR 20 continues onto the Port Townsend–Coupeville ferry which travels northeast across the Admiralty Inlet to the Keystone terminal on Whidbey Island. The ferry, operated by Washington State Ferries, takes approximately 30 minutes between terminals and runs year-round.