By the early 1930s, US 50 had been extended to San Francisco via the former US 48 by overlapping US 99 from Sacramento to Stockton and replacing US 48 over Altamont Pass to US 101E (Foothill Boulevard at Castro Valley Boulevard) near Hayward. It was extended over the new Bay Bridge at the time of its opening in 1936, replacing US 101E on Foothill Boulevard and the present MacArthur Boulevard to the Bay Bridge Distribution Structure in Oakland. As the new MacArthur Freeway (now I-580) was constructed, US 50 was moved to it. This extension was officially eliminated in the 1964 renumbering, but it remained on maps and signs for several more years before being replaced by I-80 over the Bay Bridge, I-580 over Altamont Pass, I-205 business route through Tracy, I-5 to Stockton, SR 4 (Charter Way) and SR 26 through Stockton, and SR 99 to Sacramento.