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San Francisco-Oakland Bay Bridge, California

 

Seven Modern Wonders of the World, 1955



San Francisco-Oakland Bay BridgeBuilt between 1933 and 1936, this was the longest crossing over water and most costly bridge of its time. Construction was possible due to the use of compressed-air flotation caissons. The two-mile wide West Bay was bridged by two suspension spans, linked in tandem by the world's largest bridge anchorage. ASCE designated the span an International Historic Civil Engineering Landmark in 1986. 

To meet modern earthquake standards, the west span underwent an extensive seismic retrofit that was completed in 2004. The two-mile east span is being replaced in its entirety with a new bridge featuring many of its own global innovations. Follow construction developments at the official site. 

Learn more about the history of the San Francisco-Oakland Bay Bridge.