United States Numbered Highways are the components of a national system of highways administered by the American Association of State Highway and Transportation Officials (AASHTO), a nonprofit, nonpartisan association,[3] and the various state departments of transportation.

These were initially designated on November 11, 1926, and extend throughout the contiguous United States.

Highways that exist entirely within one state.

Since the policy on numbering and designating US Highways was updated in 1991, AASHTO has been in the process of eliminating all intrastate U.S.

Highways under 300 miles (480 km) in length, "as rapidly as the State Highway Department and the Standing Committee on Highways of the American Association of State Highway and Transportation Officials can reach agreement with reference thereto"; new additions to the system must therefore serve more than one state.