San Mateo (Spanish for "Saint Matthew") is one of the 58 counties in the state of California. It was created in 1856 from the southern part of San Francisco County. In 1868 a portion of Santa Cruz County was transferred to San Mateo. The county seat is Redwood City, and the largest city is Daly City.
The county is bordered on the north by San Francisco County, the south by Santa Cruz County, on the southeast by Santa Clara County and has two bridge connections on the east to Alameda County. As of the 2010 census the population was 718,451, up from 707,161 in 2000. The county has an area of 741.01 square miles (1,919.2 km2), of which 449.07 (1,163.1 km2) is land. San Mateo is one of the traditional nine Bay Area counties.
- Although San Mateo has become separate from San Francisco County, it's airport is in San Mateo