Map of the United States showing the U.S. Highway System.

The United States Numbered Highway System (U.S. Highway System, often called U.S. Routes or U.S. Highways) is an integrated network of roads and highways numbered within a nationwide grid in the contiguous United States. As the designation and numbering of these highways were coordinated among the states, they are sometimes called Federal Highways, but the roadways were built and have always been maintained by state or local governments since their initial designation in 1926.

The route numbers and locations are coordinated by the American Association of State Highway and Transportation Officials (AASHTO). The only federal involvement in AASHTO is a nonvoting seat for the United States Department of Transportation. Generally, north-to-south highways are odd-numbered, with lowest numbers in the east, and highest in the west. Similarly, east-to-west highways are typically even-numbered, with the lowest numbers in the north, and highest in the south. Major north–south routes have numbers ending in "1" while major east–west routes have numbers ending in "0". Three-digit numbered highways are generally spur routes of parent highways (thus U.S. Route 264 is a spur off of U.S. Route 64). Some divided routes (such as U.S. Route 19E and U.S. Route 19W) exist to provide two alignments for one route. Special routes, which can be labeled as alternate, bypass or business, depending on the intended use, provide a parallel routing to the mainline U.S. Highway.

Before the U.S. Routes were designated, auto trails designated by auto trail associations were the main means of marking roads through the United States. In 1925, the Joint Board on Interstate Highways, recommended by the American Association of State Highway Officials (AASHO), worked to form a national numbering system to rationalize the roads. After several meetings, a final report was approved by the U.S. Department of Agriculture in November 1925. They received complaints from across the country about the assignment of routes, so the Board made several modifications; the U.S. Highway System was approved in November 1926. As a result of compromises made to get the U.S. Highway System approved, many routes were divided, with alignments to serve different towns. In subsequent years, AASHTO called for such splits in U.S. Routes to be eliminated.

Expansion of the system continued until 1956, when the Interstate Highway System was formed. After construction was completed, many U.S. Routes were replaced by Interstate Highways for through traffic. Despite the Interstate system, U.S. Highways still form many important regional connections, and new routes are still being added.

U.S. Route sign

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The U.S. Highway System, indicated by a white shield with black numbers, is based on a numbering grid, with odd-numbered routes running north-south and even-numbered routes running east-west. Primary routes have a one- or two-digit number, and are supplemented by spur routes that add a hundreds digit to their parent route. Routes increase from east-to-west and north-to-south, such that U.S. Route 1 follows the Atlantic Seaboard fall line, while U.S. Route 101 does the same at the Pacific Ocean Coast. Likewise U.S. Route 2 runs near the Canadian border, while U.S. Route 98 follows the Gulf Coast. Major cross-country routes end in either a "1" or a "0". For example, U.S. Route 20 is a route that runs over 3,000 miles (4,800 km) from Boston, Massachusetts, to Newport, Oregon, while U.S. Route 41 spans the country from Miami, Florida, to the Upper Peninsula of Michigan. Routes like U.S. Route 141 and U.S. Route 441 branch off U.S. Route 41. The now defunct U.S. Route 66, known as the "Mother Road", was a cultural touchstone that inspired literature, songs, and other media.

See also

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Primary U.S. Highways
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1234567891011121314151617181920212223242526272829303132333435363738394041424344454647 • 48 (CAWV–MDWV–VA) • 4950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495 • 96 (1926–19391939–Current) • 979899101163400412425
Primary routesAuxiliary routesDivided routesSpecial routesIntrastate routesFormer routesIntrastateHypothetical (AuxiliarySpecial)
Major U.S Routes are written in bold. Former U.S. Routes that are no longer part of the system are written in italic.
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