County in California
San Mateo County officially the County of San Mateo, is a county located in the U.S. state of California. As of the 2010 census, the population was 718,451. The county seat is Redwood City.
San Mateo County is included in the San Francisco–Oakland–Berkeley, 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.