<Tr> <Th> Area codes </Th> <Td> 408 / 669, 415 / 628, 510, 650, 707, 925 </Td> </Tr> <P> The San Francisco Bay Area (referred to locally as the Bay Area) is a populous region surrounding the San Francisco, San Pablo and Suisun estuaries in the U.S. state of California . Although the exact boundaries of the region vary depending on the source, the Bay Area is generally accepted to include the nine counties that border the aforementioned estuaries: Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, and Sonoma . Other sources may exclude parts of or even entire counties, or include neighboring counties such as San Benito, San Joaquin, and Santa Cruz . </P> <P> Home to approximately 7.68 million people, Northern California's nine - county Bay Area contains many cities, towns, airports, and associated regional, state, and national parks, connected by a complex multimodal transportation network . The larger combined statistical area of the region, which includes twelve counties, is the second - largest in California (after the Greater Los Angeles area), the fifth - largest in the United States, and the 41st - largest urban area in the world with 8.75 million people . The Bay Area's population is ethnically diverse: for example, roughly half of the region's residents are Hispanic, Asian, African American, or Pacific Islander, all of whom have a significant presence throughout the region . </P> <P> The earliest archaeological evidence of human settlements in the Bay Area dates back to 3000 BC . In 1769, the Bay Area was inhabited by the Ohlone people when a Spanish exploration party led by Gaspar de Portolà entered the Bay--the first documented European visit to the Bay Area . After Mexico established independence from Spain in 1821, the region was briefly controlled by the Mexican government until the United States seized the territory in 1846 during the Mexican--American War . Soon after, discovery of gold in California attracted a flood of treasure seekers, many using ports in the Bay Area as an entry point . During the early years of California's statehood, state legislative business rotated between three locations in the Bay Area before a permanent state capital was established in Sacramento . A major earthquake leveled the city of San Francisco and environs in 1906, but the region quickly rebuilt in time to host the 1915 Panama - Pacific Exposition . During World War II, the Bay Area played a major role in America's war effort in the Asiatic - Pacific Theater, with San Francisco's Fort Mason acting as a primary embarkation point for American forces . In 1945, the United Nations Charter was signed in San Francisco, establishing the United Nations, and in 1951, the Treaty of San Francisco officially ended the U.S.'s war with Japan . Since then, the Bay Area has experienced numerous political, cultural and artistic movements, developing unique local genres in music and art and establishing itself as a hotbed of progressive politics . Economically, the post-war Bay Area saw huge growth in the financial and technology industries, creating a vibrant and diverse economy with a gross domestic product of over $700 billion, and home to the second highest concentration of Fortune 500 companies in the United States . </P>

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