bus on the former U.S. Route 99, California, circa 1940

U.S. Route 99 (US 99) was the main north–south numbered highway on the West Coast until 1964, and ran from Calexico, California, on the U.S.–Mexico border to Blaine, Washington, on the U.S.-Canada border. The route was assigned in 1926 and existed until it was replaced for the most part by Interstate 5.