The tunnels (and Figueroa Street north of them) were part of pre-1964 Legislative Route 165, defined in 1933. By 1942, U.S. Route 6, U.S. Route 66, U.S. Route 99 and State Route 11 were signed through them. US 66 continued along the Arroyo Seco Parkway, while US 6 and US 99 turned northwest on San Fernando Road via Figueroa Street and Avenue 26, and SR 11 exited at Figueroa Street to run to Pasadena with U.S. Route 66 Alternate. US 99 moved to the new Golden State Freeway, bypassing the tunnels with Interstate 5, when it opened in 1962. US 6 and US 66 were removed from the Los Angeles area in the 1964 renumbering, leaving only SR 11 through the tunnels (and on the Parkway after 1964). SR 11 became State Route 110 in 1981, when the Harbor Freeway section of it became Interstate 110.