Contra Costa County, California in the context of "Berkeley, California"

The San Francisco Bay Area, commonly known as the Bay Area, is a region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose. The Association of Bay Area Governments defines the Bay Area as including the nine counties that border the estuaries of San Francisco Bay, San Pablo Bay, and Suisun Bay: Alameda, Contra Costa, Marin, Napa, San Mateo, Santa Clara, Solano, Sonoma, and San Francisco. Other definitions may be either smaller or larger, and may include neighboring counties which are not officially part of the San Francisco Bay Area, such as the Central Coast counties of Santa Cruz, San Benito, and Monterey, or the Central Valley counties of San Joaquin, Merced, and Stanislaus. The Bay Area is known for its natural beauty, prominent universities, technology companies, and affluence. The Bay Area contains many cities, towns, airports, and associated regional, state, and national parks, connected by a complex multimodal transportation network.

The earliest archaeological evidence of human settlements in the Bay Area dates back to 8000–10,000 BC. The oral tradition of the Ohlone and Miwok people suggests they have been living in the Bay Area for several hundreds if not thousands of years. The Spanish empire claimed the area beginning in the early period of Spanish colonization of the Americas. The earliest Spanish exploration of the Bay Area took place in 1769. The Mexican government controlled the area from 1821 until the 1848 Treaty of Guadalupe Hidalgo. Also in 1848, James W. Marshall discovered gold in nearby mountains, resulting in explosive immigration to the area and the precipitous decline of the Native population. The California gold rush brought rapid growth to San Francisco. California was admitted as the 31st state in 1850. A major earthquake and fire leveled much of San Francisco in 1906. During World War II, the Bay Area played a major role in America's war effort in the Asiatic-Pacific Theater, with the San Francisco Port of Embarkation, of which Fort Mason was one of 14 installations and location of the headquarters, acting as a primary embarkation point for American forces. 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. The postwar Bay Area saw large growth in the financial and technology industries, creating an economy with a gross domestic product of over $700 billion. In 2018 it was home to the third-highest concentration of Fortune 500 companies in the United States.

An unincorporated area is a parcel of land that is not governed by a local general-purpose municipal corporation. They may be governed or serviced by an encompassing unit (such as a county) or another branch of the state (such as the military). There are many unincorporated communities and areas in the United States and Canada, but many countries do not use the concept of an unincorporated area.

The Association of Bay Area Governments (ABAG) is a regional planning agency incorporating various local governments in the San Francisco Bay Area in California. It encompasses nine counties surrounding the San Francisco Bay. Those counties are Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, and Sonoma. It has the ability to establish housing and transportation goals for cities to minimize urban sprawl by requiring that housing be zoned for near new workplace construction. It deals with land use, housing, environmental quality, and economic development. Non-profit organizations as well as governmental organizations can be members. All nine counties and 101 cities within the Bay Area are voluntary members of ABAG.

As an advisory organization, ABAG has limited statutory authority. It is governed by its General Assembly, which consists of an elected official (delegate) from each city and county which is a member of the organization. The General Assembly determines policy, adopts the annual budget and work program, and reviews policy actions taken or proposed by the organization's Executive Board. A majority of city and county votes are required for action.

Suisun Bay (/səˈsuːn/ sə-SOON; Wintun for "where the west wind blows") is a shallow tidal estuary (a northeastern extension of the San Francisco Bay) in Northern California. It lies at the confluence of the Sacramento River and San Joaquin River, forming the entrance to the Sacramento–San Joaquin River Delta, an inverted river delta. To the west, Suisun Bay is drained by the Carquinez Strait, which connects to San Pablo Bay, a northern extension of San Francisco Bay. Grizzly Bay forms a northern extension of Suisun Bay. Suisun Bay is between Contra Costa County to the south and Solano County to the north.

The bay was named in 1811 after the Suisunes, a Patwin tribe of Wintun people.

San Joaquin County (/ˌsæn hwɑːˈkiːn/ SAN whah-KEEN; Spanish: San Joaquín, meaning "St. Joachim"), officially the County of San Joaquin, is a county located in the U.S. state of California. As of the 2020 United States census, the population was 779,233. The county seat is Stockton.

San Joaquin County comprises the Stockton–Lodi–Tracy metropolitan statistical area within the regional San Jose–San Francisco–Oakland combined statistical area. The county is located in Northern California's Central Valley just east of the very highly populated nine-county San Francisco Bay Area region. It is separated from the East Bay partly by the Diablo Range, through which there is road and rail access to Alameda County via the Altamont Pass, and partly by the Sacramento-San Joaquin Delta, through which there are links to Contra Costa County via road, rail, and shipping, and to Solano County via road. One of the smaller counties by area in California, it has a high population density and is growing rapidly due to overflow from the Bay Area.

Contra Costa Centre is an unincorporated community and census-designated place in Contra Costa County, California. Contra Costa Centre sits at an elevation of 92 feet (28 m). The 2010 United States census reported Contra Costa Centre's population was 5,364, while the 2020 census figure was 6,808. Contra Costa Centre is served by the Pleasant Hill / Contra Costa Centre BART station.

It is the successor to the Waldon CDP of the 2000 census.

37°42′N 122°00′W / 37.7°N 122°W / 37.7; -122

The East Bay is the eastern region of the San Francisco Bay Area and includes cities along the eastern shores of San Francisco Bay and San Pablo Bay. The region has grown to include inland communities in Alameda and Contra Costa counties. With a population of roughly 2.8 million in 2024, it is the most populous subregion in the Bay Area, containing the second- and third-most populous Bay Area counties of Alameda (1.7 million) and Contra Costa (1.1 million).