Contra Costa County, California, USA

Contra Costa County lies in the East Bay region of the San Francisco Bay Area in Northern California. Martinez is the county seat, and Mount Diablo is a prominent landmark in its interior. Waterfront areas along San Francisco, San Pablo and Suisun bays have long supported refineries, chemical plants and other industry. Agricultural communities occupy parts of the county’s eastern area. Created in 1850 as one of California’s original counties, Contra Costa takes its name from the Spanish phrase for the opposite coast, referring to its position across the bay.