Carquinez Bridge, Spanning Carquinez Strait at Interstate 80, Vallejo, Solano County, CA

Significance: The Caquinez Bridge is a cantilever truss structure which carries three lanes of westbound Interstate-80 traffic across the Carquinez Strait. (Eastbound I-80 traffic is carried by a parallel structure, erected in 1958.) The 1927 bridge was the first major auto bridge in the San Francisco Bay Area, predating by a decade the Golden Gate and San Francisco-Oakland Bay Bridges. Replacing an auto ferry across the Carquinez Strait, the bridge was an important link in north-south traffic from the Bay Area to Northern California and the Pacific Northwest, as well as connecting the Bay Area to Sacramento and points east. The bridge's importance as a north-south link diminished somewhat with the opening of the Golden Gate Bridge in 1937, but it remains a critical highway link between the Bay Area and Sacramento, carrying an average of more than fifty thousand vehicles per day. With two main spans of 1100' each, the Carquinez Bridge at the time of its completion was the fourth largest cantilever truss bridge in the world, and the second largest in the United States. (The Queensboro Bridge in New York City, constructed in 1909, was the largest cantilever truss bridge in the U.S., with spans of 984' and 1182'.) Only five bridges of any type in the U.S. had spans exceeding 1100' in 1927 (the four being suspension spans). The Carquinez Bridge was the largest bridge west of the Mississippi River, and the first major bridge designed to resist seismic forces. One of the biggest challenges for the engineers was the construction of piers in the deep and swift waters of the Carquinez Strait. Two of the bridge's piers extend approximately 135' below mean high water to bedrock, through 80'-90' of water and 45'-55' of earth beneath the channel. These were the deepest water piers ever constructed at that time, a record later surpassed by the Golden Gate and San Francisco-Oakland Bay Bridges.
Survey number: HAER CA-297
Building/structure dates: 1923-1927 Initial Construction
Building/structure dates: 1958 Subsequent Work
Building/structure dates: 1974 Subsequent Work