Geographic Regions and Area Codes

The San Francisco Bay Area is a diverse and expansive region in Northern California, encompassing nine counties: Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, and Sonoma. This area covers approximately 7,000 square miles. The region is served by multiple area codes, reflecting its large and diverse population:

  • 415/628: San Francisco and Marin counties
  • 408/669: Santa Clara County
  • 510/341: East Bay, including Oakland and Berkeley
  • 650: San Mateo County
  • 707: North Bay, including Napa and Sonoma counties
  • 925: Contra Costa County

These area codes are essential for businesses to establish a local presence and connect with customers across the region.