The San Francisco Bay Area (commonly called the Bay Area) is a greater metropolitan area in Northern California, defined locally as the nine counties that border on San Francisco Bay, including the northern extension called San Pablo Bay. These counties are Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano and Sonoma. This area includes the cities of San Francisco, Oakland and (in the "South Bay") Silicon Valley with its center at San Jose.
A more expansive definition of the Bay Area includes three additional counties that are contiguous with the nine Bay counties and comprise a logical economic metropolitan area; for instance many workers live in these three counties and commute to jobs in the Bay counties. These additional counties are San Benito, San Joaquin and Santa Cruz. This twelve-county area is also called the "San Jose-San Francisco-Oakland, CA Combined Statistical Area."
In the 1990 census, San Jose overtook San Francisco as the Bay Area's most populous city; nevertheless, San Francisco remains the cultural and historic capital of the area and the name "San Francisco Bay Area" is not in jeopardy.