The routes listed in the article were not yet numbered, or arranged in their final configuration as part of interstate routes: The September 1925 issue of New Mexico Highway Journal listed routes that had been identified during the final conference in August of the Joint Board on Interstate Highways in Washington. 666, the New Mexico designations are of interest. Three-digit numbers were assigned to alternate routes and branches of main roads.įor the history of U.S. Transcontinental and main east-west roads were assigned two-digit numbers ending in zero, while the main north-south routes carried numbers ending in one. East-west roads were given even numbers north-south roads, odd. The numbering plan devised by the Joint Board on Interstate Highways had several components.

This is the story of why it was numbered U.S. At the request of State transportation officials, the route became U.S. 666 in Arizona, Colorado, and New Mexico. On May 31, 2003, the American Association of State Highway and Transportation Officials approved a new number for the remaining segments of U.S.