The City and County of San Francisco is the fourth most populous city in California and the 13th most populous city in the United States, with a 2007 estimated population of 799,183. The second most densely populated major city in the U.S., it is the financial, cultural, and transportation center of the larger San Francisco Bay Area, a region of more than 7 million people. The city is located at the northern end of the San Francisco Peninsula with the Pacific Ocean to the west and San Francisco Bay to the east.

In 1776, the Spanish established a fort at the Golden Gate and a mission named for Francis of Assisi. The California Gold Rush in 1848 propelled the city into a period of rapid growth, transforming it into the largest city on the West Coast at the time. After being devastated by the 1906 eathquake and fire, San Francisco was quickly rebuilt, hosting the Panama-Pacific International Expansion nine years later. During World War II, San Francisco was the send-off point for many soldiers to the Pacific Theater. After the war, the confluence of returning servicemen, massive immigration, liberalizing attitudes, and other factors gave rise to the Summer of Love and the gay rights movement, cementing San Francisco as a liberal bastion in the United States.

San Francisco is a popular international tourist destination renowned for its chilly summer fog, steep rolling hills, eclectic mix of Victoria and modern architecture and its famous landmarks, including the Golden Gate Bridge, the cable cars, and Chinatown. The city is also known for its diverse, cosmopolitan population, including large and long-established Asian American and LGBT communities.