The Twin Peaks Tunnel is a light rail/streetcar tunnel in San Francisco, California. The tunnel runs under Twin Peaks and is used by the K Ingleside, M Ocean View and S Shuttle lines of the Muni Metro system. The eastern entrance to the tunnel is located at the west end of the Market Street subway near the intersection of Market and Castro streets in the Castro neighborhood, and the western entrance is located at West Portal Avenue and Ulloa Street in the West Portal neighborhood, named for the tunnel. There are three stations along the tunnel, West Portal at the western entrance, Forest Hill near the middle, and the now disused Eureka Valley near the eastern end. History Plans for a tunnel extending from Market Street under Twin Peaks were first presented at the Merchants' Association banquet in May 1909; A. W. Scott Jr. spoke on the need for the tunnel to open up the western part of San Francisco to development, as "40,000 San Franciscans lived across the bay or in San Mateo county because of the lack of proper transportation in this city." In April 1910, a committee named the Twin Peaks Convention was formed to plan the project, which would open the development of approximately one quarter of San Francisco's land area. Competing proposals In July 1910 an architectural rendering was released of the eastern portal; the tunnel was initially envisioned as a two-story bore long, carrying road traffic on the upper deck and rail traffic on the lower deck. Market Street would be extended southwest in a straight line across private property to connect to the eastern portal, to be located at the intersection of 19th and Douglass. Initial estimates for the cost of the tunnel ranged from in 1909 to in 1910. The Twin Peaks Tunnel and Improvement Convention released their report in August 1910 recommending a municipal bond to pay for the tunnel, whose costs would be recouped by the additional taxation of the land that would then be opened for development. Other options were considered and rejected, including a special assessment district or a long-term railroad lease. The San Francisco Board of Supervisors approved a competing plan to build a longer tunnel under Twin Peaks in March 1912, continuing under Market to Valencia, which was seen as the foundation for a rapid transit system connecting the downtown Financial District with western San Francisco