28, 1912, when the San Francisco Municipal Railway (Muni) was established. The first streetcar line, the A Geary, ran from Kearny and Market Streets in the Financial District to Fulton Street and 10th Avenue in the Richmond District. The system slowly expanded, opening the Twin Peaks Tunnel in 1917, allowing streetcars to run to the southwestern quadrant of the city. By 1921, the city was operating of electric trolley lines and of cable car lines. The last line to start service before 2007 was the N Judah, which started service after the Sunset Tunnel opened in 1928. In the 1940s and 1950s, as in many North American cities, public transit in San Francisco was consolidated under the aegis of a single municipal corporation, which then began phasing out much of the streetcar network in favor of buses. However, five heavily used streetcar lines traveled for at least part of their routes through tunnels or otherwise reserved right-of-way, and thus could not be converted to bus lines. As a result, these lines, running PCC streetcars, continued in operation. Market Street subway Original plans for the BART system drawn up in the 1950s envisioned a double-decked subway tunnel under Market Street (known as the Market Street subway) in downtown San Francisco; the lower deck would be dedicated to express trains, while the upper would be served by local trains whose routes would spread south and west through the city. However, by 1961 these plans were altered; only a single BART route would travel through the city on the lower deck, while the upper deck would be served by the existing Muni streetcar routes. The new tunnel would be connected to the existing Twin Peaks Tunnel. The new underground stations would feature high platforms, and the older stations would be retrofitted with the same, which meant that the PCCs could not be used in them. Hence, a fleet of new light rail vehicles was ordered from Boeing-Vertol, but were not delivered until 1979–80, even though the tunnel was completed in 1978. The K and M lines were extended to Balboa Park during this time, providing further connections to BART. (The J line also saw an extension there in 1991, which provided yet another BART connection at Glen Park.) On February 18, 1980, the Muni Metro was officially inaugurated, with weekday N line service in the subway. The Metro service was implemented in phases,