San Francisco Bay Area

The San Francisco Bay Area, sometimes referred to as The Bay Area, is a metropolitan area that lies along the San Francisco Bay in northern California, with an estimated population of 7.15 million people. Its area is often defined as the area covered by the nine counties that border either San Francisco Bay or San Pablo Bay: Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, and Sonoma. By this definition, the Bay Area has a population of over seven million residents, making it the second largest metropolitan area west of the Mississippi. Santa Cruz County is sometimes considered a member of the Bay Area as well. It does not adjoin the San Francisco Bay, but has strong cultural ties to the Bay Area.

This nine- or ten-county area consists of cities of various size that lie more or less contiguously around the length of the bay. Three large cities dominate the area: San Francisco, San Jose, and Oakland. Because, unlike most other metropolitan areas in the United States, no single large city dominates the region, residents generally refer to the region generically as the Bay Area, without associating it with any one city. However, because San Francisco was historically the first major population center in the area, and because of its densely urbanized character in constrast to its neighbors, people in the region often refer to San Francisco as simply the City. Even San Jose natives, who live in the more populous city, will speak of "going to the City" when referring to a trip to San Francisco.

A more restrictive, informal definition includes only the urban portions of the previously defined area and also excludes Napa, Solano, and Sonoma counties, which are largely rural or suburban in character and have inland climates. High real-estate prices in this core of the Bay Area have driven many residents and businesses to move to outlying areas or to the Central Valley metropolitan areas of Sacramento, Stockton or Modesto, California area. As this trend continues, the definition of the Bay Area will likely expand, perhaps even including Yolo County as well.

The Bay Area is also host to six different major league sports.

Geography

The combined area of the nine Bay Area counties is 22,789 km² (8,798 mi²), or 21,216 km² (8,191 mi²), not including Santa Cruz County.

As well as constituting one of the world's greatest metropolitan areas, the Bay Area includes some exceptional natural coastal and rural landscape. It includes significant national parks such as the Point Reyes National Seashore, a large number of state parks including important ones like the Mount Diablo State Park, and numerous parks and preserves maintained by local government agencies - notably by the East Bay Regional Park District which has major land holdings in Alameda and Contra Costa counties. Most of these conserved areas are within easy reach of the metropolitan areas, many of them by public transportation.

Because the hills, mountains, and large bodies of water produce such vast geographic diversity within this region, the Bay Area offers a significant variety of microclimates. The areas near the Pacific Ocean are generally characterized by relatively small temperature variations during the year, with cool foggy summers and mild rainy winters. Inland areas, especially those separated from the ocean by hills or mountains, have hotter summers and colder overnight temperatures during the winter.

Subregions

The population distribution of the Bay Area is generally subdivided into several smaller subregions.

The region north of the Golden Gate Bridge is known as the North Bay. This area consists of Marin County and extends northward into Napa and Sonoma counties. With some exceptions, this region is extremely affluent, and is generally the least urbanized part of the Bay Area, with many areas of undeveloped park and farm land. It is the only section of the Bay Area that is not served by a commuter rail transit service, though Sonoma-Marin service has entered the planning phase.
The eastern side of the bay, dominated by the city of Oakland but also including Berkeley, Richmond and several small cities, is known as the East Bay. The region, partly thanks to the Bay Area Rapid Transit (BART) rail service, has extended beyond the East Bay hills into suburban communities such as Walnut Creek, Concord and Antioch. The weather on the eastern side of the hills is markedly warmer in the summer as compared to San Francisco (which tends to maintain a rather moderate climate year-round).
The communities along the southern edge of the Bay are known as the South Bay. The South Bay covers roughly the same area as Silicon Valley, although some Peninsula and East Bay towns are sometimes included in the latter. It includes the cities of San Jose, Fremont, and the high-tech hub of Santa Clara, as well as many smaller communities.
The area between the South Bay and the city of San Francisco is known as the San Francisco Peninsula, locally just as The Peninsula. This area consists of a series of small cities and suburban communities along the Bay, as well as various towns along the Pacific coast.
San Francisco is generally placed in a category by itself, separated by water from the north and east, and by county line from its neighbor cities to the South (Locals refer to San Francisco as SF or The City. It is never referred to as San Fran or Frisco.) By extension, South San Francisco is often referred to as "South City," even though there are other towns between SSF and SF.
Transportation
Airports
San Francisco International Airport (SFO)
Oakland International Airport (OAK)
Mineta San Jose International Airport (SJC)
Public transportation

Each Bay Area county operates its own bus system (see Muni, AC Transit, SamTrans, VTA, County Connection). In addition, the Bay Area is served by a number of mass transit systems:
Bay Area Rapid Transit (BART) - A rapid transit electric train service that serves parts of the Bay Area, including San Francisco, Oakland, Berkeley, Fremont, and Walnut Creek. It also serves the San Francisco and Oakland airports.
Caltrain - A commuter rail service that connects San Jose and cities along the Peninsula with San Francisco, California, and with the BART system by way of the Millbrae Transit Station.
Amtrak - There are several Amtrak stations throughout the Bay Area. In particular, a major station in Oakland provides a rail link to Sacramento by way of the Capitol Corridor.
ACE - Altamont Commuter Express; a rail service that mainly serves commuters to and from the Central Valley to the Silicon Valley. It travels from Stockton through Pleasanton, Fremont, Santa Clara, and ends at San Jose. It operates only during commute hours on weekdays.
Freeways and highways

The Bay Area possesses an extensive freeway and highway system.
Trans-bay crossings -
Interstate 80 - The western terminus of I-80 is located in San Francisco, just west of the San Francisco-Oakland Bay Bridge. The interstate continues to the east, connecting to Oakland and the north coast of the East Bay, and then on to Sacramento and Reno.
Interstate 580 - This spur route's western terminus is in Marin County. The Interstate crosses the San Pablo Bay over the Richmond-San Rafael Bridge, passes through Oakland, then continues to Livermore, through the Altamont Pass to Tracy, where it intersects with Interstate 5.
California Highway 92 - CA-92's western terminus is in Half Moon Bay. The two lane highway crosses the Peninsula, connecting to Woodside and San Mateo before crossing the San Mateo-Hayward Bridge to Hayward.
California Highway 84 - CA-84 crosses the Bay over the Dumbarton Bridge from Redwood City to Newark. The route then passes through Fremont, continuing as Niles Canyon Road to Sunol and Livermore
The Peninsula to the South Bay -
Interstate 280 and U.S. Highway 101 - 8 lane, and in some parts, 10 lane freeways connecting San Francisco to San Jose, passing through the Peninsula. Highway 101 continues south to Gilroy and Salinas, California, before continuing to Los Angeles.
California State Routes 1 and 35 - two lane highways also traveling down the Peninsula, CA-1 along the Pacific coast, and CA-35 near the ridge of the Santa Cruz Mountains. CA-1 connects to Half Moon Bay, Santa Cruz and Monterey, before continuing to Los Angeles.
California Highways 17 and 9 - highways through the Santa Cruz Mountains, connecting the South Bay to Santa Cruz. Part of CA-17 in San Jose is an 8 lane freeway.
California Highways 237 and 85 - freeways connecting the west Santa Clara Valley to the east Santa Clara Valley, bypassing Downtown San Jose.
California State Highway 87 - north-south freeway entirely in San Jose, connects Downtown to the Almaden Valley.
California State Highway 152 - two lane highway from Watsonville, crosses the Santa Cruz Mountains to Gilroy, then crosses the Diablo Range through Pacheco Pass to I-5 near Los Banos.
The freeway system in Santa Clara county is augmented by its expressway system.
Marin County -
US-101 and CA-1 - continue north of San Francisco, crossing the Golden Gate Bridge and connecting San Francisco to Marin and eventually to Oregon.
East Bay -
Interstates 880 and 680 travel up the East Bay from San Jose, 880 close to the bay to Oakland, and 680 inland through Pleasanton and Concord.
California State Highway 238/Interstate 238 (Mission Boulevard) is an arterial from Fremont to Hayward, along the base of the hills, then becomes a freeway near Oakland.
Regional counties, cities and suburbs

The following lists are based on the ten county definition of the Bay Area. Those places listed in italics would be excluded by the nine county definition which excludes Santa Cruz County.