1. United States system of numbered highways : adopted for uniform marking by the American Association of state highway officials together with the Federal Aid Highway System approved with the act of November 9, 1921 and subsequent amendments thereto Yale Public content 1950. 2010-08-10T13:55:54Z. 2015-10-27T22:25:25Z. United States. Bureau of Public Roads. Bureau of Public Roads : For sale by the Supt. of Docs., U.S. G.P.O. English. Public. United States.