The City and County of San Francisco is the fourth most populous city in California and the 14th most populous city in the United States, with a 2007 estimated population of 764,976.San Francisco is located on the west coast of the U.S. at the tip of the San Francisco Peninsula and includes significant stretches of the Pacific Ocean and San Francisco Bay within its boundaries. Several islands are part of the city, notably Alcatraz, Treasure Island, and the adjacent Yerba Buena Island, together with small portions of Alameda Island, Angel Island, and Red Rock Island. Also included are the uninhabited Farallon Islands, 27 miles (43 km) offshore in the Pacific Ocean. The mainland within the city limits roughly forms a "seven-by-seven-mile square," a common local colloquialism referring to the city's shape.
the San Francisco Municipal Railway (Muni). The city-owned system operates both a combined light rail/subway system (the Muni Metro) and a bus network that includes trolleybuses, standard diesel motorcoaches and diesel hybrid buses.
Bay Area Rapid Transit (BART) is the regional rapid transit system which connects San Francisco with the East Bay through the Transbay Tube. The line runs under Market Street to Civic Center, where it turns south to the Mission District, the southern part of the city, and through northern San Mateo County, to the San Francisco International Airport, and Millbrae.The Caltrain rail system runs from San Francisco along the Peninsula down to San Jose. The line dates from 1863, and for many years was operated by Southern Pacific.
The Transbay Terminal serves as the terminus for long range bus service (such as Greyhound) and as a hub for regional bus systems AC Transit (Alameda County), SamTrans (San Mateo County), and Golden Gate Transit (Marin and Sonoma Counties). Amtrak also runs a shuttle bus from San Francisco to its rail station in Emeryville.