San Mateo city is located San Mateo County.
San Mateo County is located in the San Francisco Bay Area of the U.S. state of California. It covers most of the south right on the San Francisco peninsula and northern Santa Clara County.
San Francisco International Airport is located at the northern end of the county, and Silicon Valley begins at the southern end. The county seat is Redwood City, the second largest Hispanic county in northern California after Santa Clara County.