The short lived segments of Interstates 105 and 110 by Downtown Los Angeles in 1966.
Interstate 110 was established again in 1978 along a different stretch of highway: the Harbor Freeway (California 11). Having been built in stages through the 1950s and 1960s, the Harbor Freeway was one of the oldest freeways in the Los Angeles Basin. The first sections were constructed as part of U.S. 6, which previously followed Figueroa Street from Downtown Los Angeles to San Pedro.
When U.S. 6 was decommissioned in 1964, the Harbor Freeway was redesignated as California 11. The state route also followed the adjacent Pasadena Freeway to the north. AASHTO approved the I-110 designation along the Harbor Freeway from California 47 to I-10 on June 25, 1979. The remainder of California 11 was renumbered California 110.
State Route 110 northeast from Chinatown to Glenarm Street in Pasadena follows one of the old alignments of U.S. 66. Built in the 1940s and 1950s, this section of SR 110 follows Arroyo Seco Parkway. Many of the original sub-standard sections of the Arroyo Seco Parkway remain, including short acceleration and deceleration lanes, stop signs at the freeway entrance ramps, minimal shoulders, the Figueroa Tunnels, sharp turns and narrow lanes. Due to its historical status, many of these features will be not be modified.
SR 110 previously extended both north of the Pasadena Freeway and south of the Harbor Freeway (I-110) along surface streets. The northern segment ran between Glenarm Street and Colorado Boulevard (former U.S. 66). It was relinquished to the city of Pasadena on August 31, 2000.1 The southern leg of SR 110 followed Gaffey Street through San Pedro. Relinquished by the state in June 2009, it connected I-110 with the cruise ship port.