Napa County is a county located north of San Pablo Bay in the U.S. state of California. It is officially one of the nine San Francisco Bay Area counties, and one of four North Bay counties. The county is coterminous with the Napa, California, Metropolitan Statistical Area. As of the 2010 census the population is 136,484. The county seat is Napa. Napa County was one of the original counties of California, created in 1850 at the time of statehood.