Napa is one of the 58 counties in the state of California. It was created in 1850, making it one of the original counties in the state. As of the 2010 census, the population was 136,484, up from 124,279 in 2000. The county seat and largest city is Napa.
The county has 788.27 (2,041.6 km2) square miles of area, of which 753.73 square miles (1,952.2 km2) is land. Napa is bordered by Sonoma County on the west, Lake County on the north, Yolo County on the east, and Solano County on the south and southeast.
Napa is one of the traditional nine Bay Area counties.