Coordinates: 37°45′N 122°17′W San Francisco Bay Area The San Francisco Bay Area, popularly referred to as the Bay Area or simply the Bay, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. Although the exact San Francisco Bay Area boundaries of the region vary depending on the source, the Bay Area is defined by the Association of Bay Area Conurbation Governments to include the nine counties that border the aforementioned estuaries: Alameda, Contra Costa, Marin, Napa, San Mateo, Santa Clara, Solano, Sonoma, and San Francisco. Other sources may exclude parts of or even entire counties, or expand the definition to include neighboring counties that do not border the bay such as San Benito, San Joaquin, and Santa Cruz. Home to approximately 7.75 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 fourteen 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 9.67 million people.[7] 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. The earliest archaeological evidence of human settlements in the Bay Area dates back to 8000–10,000 BC (from shell mounds in the Coyote Hills). 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 purchased 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 Clockwise from top: The Stanford University War II, the Bay Area played a major role in America's war effort in the Asiatic-Pacific Theater, with San Francisco's Oval, San Francisco Chinatown with the Bay Fort Mason acting as a primary embarkation point for American forces. In 1945, the United Nations Charter was Bridge in the background, Napa Valley signed in San Francisco, establishing the United Nations, and in 1951, the Treaty of San Francisco officially ended the vineyards, the Circle of Palms Plaza in San U.S.'s war with Japan. Since then, the Bay Area has experienced numerous political, cultural and artistic movements, Jose, the Golden Gate Bridge, the Palo Alto developing unique local genres in music and art and establishing itself as a hotbed of progressive politics. Baylands Nature Preserve, Oakland's Economically, the post-war Bay Area saw huge growth in the financial and technology industries, creating a vibrant downtown skyline, and redwood trees in Muir and diverse economy with a gross domestic product of over $700 billion, and home to the third highest concentration Woods of Fortune 500 companies in the United States (as of 2018).[8][9] Despite its urban character, the San Francisco Bay is one of California's most ecologically important habitats, providing key ecosystem services such as filtering pollutants and sediments from the rivers, and supporting a number of endangered species. The region is also known for the complexity of its landforms, the result of millions of years of tectonic plate movements. Because the Bay Area is crossed by six major earthquake faults, the region is particularly exposed to hazards presented by large earthquakes. The climate is temperate and generally very mild, and is ideal for outdoor recreational and athletic activities such as hiking. The Bay Area is host to six professional sports teams and is a cultural center for music, theater, and the arts. It is also host to several institutions of higher education, ranging from primary schools to major research universities. Home to 101 municipalities and nine counties, governance in the Bay Location of the Bay Area within Area is multifaceted and involves numerous local and regional actors, each with wide-ranging and overlapping California. responsibilities. The nine-county Bay Area. Additional counties in the larger fourteen-county CSA. Country United Contents States Boundaries State California Subregions Subregions East Bay History North Bay Peninsula Culture San Francisco Arts South Bay Art Music Principal cities List Theater San Jose Media San Francisco Sports and recreation Oakland Fremont Demographics Santa Rosa Crime Hayward Economy Sunnyvale Housing Concord Santa Clara Education Vallejo Colleges and universities Berkeley Primary and secondary schools Fairfield Geography Antioch Climate Richmond Ecology Daly City Marine wildlife San Mateo Birds Vacaville Geology and landforms San Leandro Hydrography Livermore Redwood City Government and politics Dublin Transportation Mountain View See also Napa References Area[1] External links • Nine-county 6,966 sq mi (18,040 km2) • CSA 10,191 sq mi Boundaries (26,390 km2) Highest elevation[2] 4,360 ft (1,330 m) The borders of the San Francisco Bay Area are not officially delineated, and the unique development patterns Copernicus Peak [3] influenced by the region's topography, as well as unusual commute patterns caused by the presence of three central Lowest elevation −13 ft (−4 m) cities and employment centers located in various suburban locales, has led to considerable disagreement between local Alviso and federal definitions of the area.[10] Because of this, professor of geography at the University of California, Population (2018) Berkeley Richard Walker claimed that "no other U.S. city-region is as definitionally challenged [as the Bay Area]."[10] • Nine-county 7.75 million[4] • Nine-county 1,113/sq mi When the region began to rapidly develop during and immediately after World War II, local planners settled on a nine- density (430/km2) county definition for the Bay Area, consisting of the counties that directly border the San Francisco, San Pablo, and • CSA 8.84 million[5] Suisun estuaries: Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, and Sonoma • CSA density 868/sq mi [11] counties. Today, this definition is accepted by most local governmental agencies including San Francisco Regional (335/km2) [12] [13] Water Quality Control Board, Bay Area Air Quality Management District, the San Francisco Bay Restoration Time zone UTC−08:00 [14] [15] [16] Authority, the Metropolitan Transportation Commission, and the Association of Bay Area Governments, the (Pacific) [17] latter two of which partner to deliver a Bay Area Census using the nine-county definition. • Summer (DST) UTC−07:00 (PDT) Various U.S. Federal government agencies use definitions that differ from their local counterparts' nine-county definition. For example, the Federal Communications Commission (FCC) which regulates broadcast, cable, and Area codes 408/669, 415/628, satellite transmissions, includes nearby Colusa, Lake and Mendocino counties in their "San Francisco-Oakland-San 510/341, 650, [18] Jose" media market, but excludes eastern Solano county. On the other hand, the United States Office of 707, 925[6] Management and Budget, which designates Metropolitan Statistical Areas (MSAs) and Combined Statistical Areas (CSA) for populated regions across the country, has five MSAs which include, wholly or partially, areas within the nine- county definition, and one CSA which includes all nine counties plus neighboring San Benito, Santa Cruz and San Joaquin counties.[19] Subregions Among locals, the nine-county Bay Area can be further divided into five sub-regions: the East Bay, North Bay, South Bay, Peninsula, and the city of San Francisco. Although geographically located on the tip of the San Francisco Peninsula, the city of San Francisco is not considered part of the "Peninsula" subregion, but as a separate entity.[20][21] The "East Bay" is the densest region of the Bay Area outside of San Francisco and includes cities and towns in Alameda and Contra Costa counties, centered around Oakland. As one of the larger subregions, the East Bay includes a variety of enclaves, including the suburban Tri-Valley area and the highly urban western part of the subregion that runs alongside the bay.[22] The "Peninsula" subregion includes the cities and towns on the San Francisco Peninsula, excluding the titular city A map of the locally accepted nine- of San Francisco. Its eastern half, which runs alongside the Bay, is highly populated while its less populated western coast county definition of the Bay Area. traces the coastline of the Pacific Ocean and is known for its open space and hiking trails. Roughly coinciding with the Also displayed are the five borders of San Mateo county, it also includes the northwestern Santa Clara county cities of Palo Alto, Mountain View, and subregions of the Bay Area, which are divided along county lines except Los Altos.[23] The "South Bay" includes all of the rest of the cities in Santa Clara county, centered around San Jose, the [24] for the northwestern portion of Santa largest city in Northern California. It is roughly synonymous with Silicon Valley due to its high concentration of tech Clara county. companies, although the industry also has a significant presence in the rest of the Bay Area.[25] The "North Bay" includes Marin, Sonoma, Napa, and Solano counties, and is the largest and least populated subregion.