U.S. Route 40 or U.S. Highway 40 (US 40), also known as the Main Street of America, is a major east–west United States Highway traveling across the United States from the Mountain States to the Mid-Atlantic States. As with most routes whose numbers end in a zero, US 40 once traversed the entire United States. It is one of the first U.S. Highways created in 1926 and its original termini were in San Francisco, California, and Atlantic City, New Jersey. US 40 currently ends at a junction with I-80 in Silver Summit, Utah, just outside Salt Lake City. West of this point US 40 was functionally replaced with I-80, and as these segments of I-80 were constructed the western portion of US 40 was truncated several times. 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. US 40 passes through or by major cities including Denver, Kansas City, St. Louis, Indianapolis, Columbus, Baltimore, and Wilmington. Three former and four current state capitals lie along the route. For much of its route, US 40 runs parallel to or concurrently with several major Interstate Highways: I-70 from Denver, Colorado, to Washington, Pennsylvania; and again from Hancock, Maryland to Baltimore; I-64 in parts of Missouri and Illinois; I-68 along the Maryland Panhandle; and I-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. 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 Black Horse Pike in New Jersey, part of the Oregon Trail in Kansas, and the Lincoln Highway throughout most of California.
