37.44, -122.36
San Mateo County ( SAN mə-TAY-oh), officially the County of San Mateo, is a county located in the U.S. state of California. As of the 2020 census, the population was 764,442. Redwood City is the county seat, and the third most populated city following Daly City and San Mateo. San Mateo County is included in the San Francisco–Oakland–Berkeley, CA MSA (metropolitan statistical area), Silicon Valley, and is part of the San Francisco Bay Area, the nine counties bordering San Francisco Bay. It covers most of the San Francisco Peninsula. San Francisco International Airport is located in the northeastern area of the county and is approximately 7 miles (11 km) south of the city and county limits of San Francisco, even though the airport itself is assigned a San Francisco postal address. The county's built-up areas are mostly suburban, and are home to many corporate campuses.