U.S. Route 40

U.S. Route 40 (US 40) is an east–west United States highway. As with most routes whose numbers end in a zero, US 40 once traversed the entire United States. It is one of the original 1920s U.S. Highways, and its first termini were San Francisco, California, and Atlantic City, New Jersey. The western end has been truncated several times, and the route now ends at Interstate 80 just outside of Park City, Utah, near Salt Lake City.

Starting at its western terminus in Utah, US 40 crosses a total of 12 states, including Colorado, Kansas, Missouri, Illinois, Indiana, Ohio, West Virginia, Pennsylvania, Maryland, Delaware, and New Jersey. Three former and four current state capitals lie along the route.a For much of its route, US 40 runs parallel to or concurrently with several major Interstate Highways: Interstate 70 from Colorado, to Washington, Pennsylvania; and again from Hancock, Maryland to Baltimore, Maryland; Interstate 64 in parts of Missouri and Illinois; Interstate 68 along the Maryland Panhandle; and Interstate 95 from Baltimore to New Castle, Delaware.

The route was built on top of several older highways, most notably the National Road and the Victory Highway. The National Road was created in 1806 by an act of Congress to serve as the first Federally funded highway construction project. When completed it connected Cumberland, Maryland, with Vandalia, Illinois. The Victory Highway was designated as a memorial to World War I veterans and ran from Kansas City, Missouri to San Francisco, California. Other important roads that have become part of US 40 include Zane's Trace in Ohio, Braddock Road in Maryland and Pennsylvania, part of the Oregon Trail in Kansas, and the Lincoln Highway (the first road across America) in California.