Alameda County is a county in California. It occupies most of the East Bay region of the San Francisco Bay Area. The county has a total area of 821 mi². The San Francisco Bay borders the county on the west. The crest of the Berkeley Hills form part of the northeastern boundary, and reach into the center of the county. A coastal plain several miles wide lines the bay, being home to Oakland and the most populated regions. Livermore Valley lies in the eastern part of the county. As of the 2000 census it had a population of 1,443,741 making it the 7th largest county in the state. The county seat is Oakland.