Key System Mole

 mole, historical layer / disappeared object

The eastern side of the Bay Bridge follows the original route of and is built upon landfill used by the Key System causeway and mole (ferry piers located at the end of the causeway carrying the railbed), which provided service between San Francisco and East Bay between 1903 and 1958. After the Bay Bridge was completed in 1938, Key System streetcars ran on the lower deck of the bridge until the system's dismantlement.

The mole stretched almost to Yerba Buena Island. The mole's terminal was roughly located near the section of bridge which collapsed in the Loma Prieta quake. This section burned on May 6, 1933, taking the ferryboat Peralta, 50 rail cars, and over 500 feet of pier with it. The Peralta's hulk was rebuilt as the Kalakala and returned to service in 1935 in Puget Sound.