San Mateo County

San Mateo County is a county on the San Francisco Peninsula in California, stretching between the Pacific Ocean to the west and San Francisco Bay to the east. The county includes several cities and towns, with Redwood City serving as its administrative seat, alongside coastal stretches and forested ridges running along the peninsula.

The county was formed in 1856 through the division of what was then San Francisco County and took its name from the Spanish missionary Mateo. Redwood City was designated as the county seat the following year and has remained the administrative center since.

The area maintains 22 parks, trails, and historic sites, including Memorial Park and Fitzgerald Marine Reserve, preserving natural and cultural heritage.

Travelers can reach the county via the Caltrain commuter rail or the BART subway system, both connecting several cities across the peninsula. Bus routes operated by SamTrans complement the rail options and cover routes not directly served by the train systems.

San Francisco International Airport technically sits within the boundaries of this county, even though it carries the name of the neighboring city. Many visitors do not realize they are already landing in San Mateo County before continuing on to San Francisco.

Location: California

Inception: 1856

Capital city: Redwood City

Part of: San Francisco–San Mateo–Redwood City metropolitan division

Shares border with: Alameda County, San Francisco County, Santa Clara County, Santa Cruz County

Phone: +16503634000

Website: http://smcgov.org

GPS coordinates: 37.44000,-122.36000

Latest update: December 4, 2025 19:03