The 1906 earthquake damaged many cable car and streetcar lines ; in the aftermath , the United Railroads ( URR ) closed many cable cars lines and expanded the electric streetcar system . The URR resumed service on the Ocean Avenue ( 12 ) line on May 6 , 1906 ; the line was soon extended to Ocean Beach via Junipero Serra Boulevard and Sloat Boulevard . The city-owned Twin Peaks Tunnel was opened on February 3 , 1918 , with the K Ingleside line running through the tunnel and terminating at St. Francis Circle to avoid crossing the existing private tracks . In November 1918 , the San Francisco Municipal Railway reached an agreement with the URR to allow the city 's streetcars to use Market Street Railway trackage . The K Ingleside line was thus extended southwards from St. Francis Circle on Junipero Serra Boulevard and east on Ocean Avenue on February 21 , 1919 . M Ocean View service began on October 6 , 1925 ; the new line split from the existing tracks in the circle and ran southwest on a private right-of-way . The city purchased the private company ( renamed Market Street Railway in 1921 ) in 1944 ; route 12 streetcar service ended on April 8 , 1945 , leaving just the K Ingleside on Junipero Serra Boulevard
1906 earthquake
1906 San Francisco earthquake
St. Francis Circle station