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. Among the most densely populated cities in the country, San Francisco is part of the San Francisco Bay Area metropolitan area, which is home to more than 7.2 million people. The city is located at the tip of the San Francisco Peninsula, with the Pacific Ocean to the west, San Francisco Bay to the east, and the Golden Gate to the north.
San Francisco's climate is characteristic of California’s Mediterranean climate with mild, wet winters and dry summers. In addition, since it is surrounded on three sides by water, San Francisco's climate is strongly influenced by the cool currents of the Pacific Ocean which tends to moderate temperature swings and produce a remarkably mild climate with little seasonal temperature variation. Average summertime high temperatures in San Francisco peak at 70 °F (21 °C) and are 20 °F (9 °C) lower than in nearby inland locations like Livermore. Lows almost never reach freezing temperatures, though the lowest temperature ever recorded in San Francisco was 27 °F (−3 °C) on December 11, 1932. May through September is very dry, but rain is common from November through March. Snowfall is extraordinarily rare, with only 10 instances recorded since 1852. The combination of cold ocean water and the high heat of the California mainland create the city's characteristic fog that can cover the western half of the city all day during the spring and early summer. The fog is less pronounced in eastern neighborhoods, in the late summer, and during the fall, which are the warmest months of the year. Due to its sharp topography and maritime influences, San Francisco exhibits a multitude of distinct micro-climates. The high hills in the geographic center of the city are responsible for a 20 percent variance in annual rainfall between different parts of the city. They also protect neighborhoods directly to their east from the foggy and cool conditions experienced in the Sunset District; for those who live on the eastern side of the city, San Francisco is sunnier, with an average of 260 clear days, and only 105 cloudy days per year.
In 1776, the Spanish settled the tip of the peninsula, establishing 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 earthquake and fire, San Francisco was quickly rebuilt, hosting the Panama-Pacific International Exposition 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 characterized by a high standard of living. The great wealth and opportunity generated by the Internet revolution continues to draw many highly educated and high-income workers and residents to San Francisco. Numerous lower-income neighborhoods consequently have become increasingly gentrified, and many of the city's traditional business and industrial districts have experienced a renaissance driven by the redevelopment of the Embarcadero, including the neighborhoods South Beach and Mission Bay. The city's property values and household income have escalated to among the highest in the nation, allowing the city to support a large restaurant and entertainment infrastructure. Because the cost of living in San Francisco is exceptionally high, many middle class families have decided they can no longer afford to live within the city and have left.
San Francisco is a popular international tourist destination famous for its landmarks, including the Golden Gate Bridge, Alcatraz Island, the cable cars, Coit Tower, and Chinatown, its steep rolling hills, and its eclectic mix of Victorian and modern architecture. The city is also known for its diverse, cosmopolitan population, including large and long-established Asian American, and LGBT communities.