The M Ocean View line began operation on October 6, 1925, as a shuttle service from St. Francis Circle to the wye at Broad and Plymouth in the city's Ocean View District. It was extended through the Twin Peaks Tunnel to the downtown Ferry Building on October 31, 1927, but reverted to a shuttle service on February 27, 1928. The shuttle service was replaced by buses on August 6, 1939, but streetcar service returned on the full length of the line on December 17, 1944. On June 6, 1948, the Transbay Terminal became the inner terminus of the line.
