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 and is separated from the Bay Area by the Diablo Range of low mountains with its Altamont Pass. One of the smaller counties in area in California, it has a high population density and is growing rapidly due to overflow from the Bay area's need for housing.