Here are a few from my personal collection. The first postcard is postmarked 1922 and shows the SP railroad ferry (info below). The others date between 1900 and 1920.
Southern Pacific Railroad - Ferryboat "Solano" Port Costa
Benicia, California - Largest Ferry Boat in the world.
Benicia, California - Largest Ferry Boat in the world.
San Francisco Bay - The San Francisco Belt Railroad had slip at Pier 43 which allowed interchange with the Northwestern Pacific, the Western Pacific, and the Atchison, Topeka and Santa Fe railroads.
Suisun Bay - The Central Pacific Railroad built a ferry that operated between Benicia and Port Costa, California from 1879 to 1930. (Southern Pacific)