instruction: What was the primary mode of transportation across the San Francisco bay prior to the Golden Gate Bridge?
context: Before the bridge was built, the only practical short route between San Francisco and what is now Marin County was by boat across a section of San Francisco Bay. A ferry service began as early as 1820, with a regularly scheduled service beginning in the 1840s for the purpose of transporting water to San Francisco.
  
  The Sausalito Land and Ferry Company service, launched in 1867, eventually became the Golden Gate Ferry Company, a Southern Pacific Railroad subsidiary, the largest ferry operation in the world by the late 1920s. Once for railroad passengers and customers only, Southern Pacific's automobile ferries became very profitable and important to the regional economy. The ferry crossing between the Hyde Street Pier in San Francisco and Sausalito Ferry Terminal in Marin County took approximately 20 minutes and cost $1.00 per vehicle,[when?] a price later reduced to compete with the new bridge. The trip from the San Francisco Ferry Building took 27 minutes.
response: The only (practical) way to get across the San Francisco Bay prior to 1937 was by Ferry. The Golden Gate Ferry Company, which became the largest ferry operation by the late 1920's, was established in 1867 as the Sausalito Land & Ferry Company. The ferry would take approximately 20 minutes and cost $1.00 per vehicle.