San Mateo County (Spanish for "Saint Matthew") is a county located in the U.S. state of California. As of the 2010 census, the population of San Mateo County was 718,451. The county seat is Redwood City.
San Mateo County is included in the San Francisco-Oakland-Hayward, CA Metropolitan Statistical Area, 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 at the northern end of the county, and Silicon Valley begins at the southern end. The county's built-up areas are mostly suburban with some areas being very urban, and are home to several corporate campuses.