San Mateo County is a county located in the San Francisco Bay Area of the U.S. state of California. It covers most of the San Francisco Peninsula just south of San Francisco, and north of Santa Clara County. San Francisco International Airport is located at the northern end of the county, and Silicon Valley begins at the southern end. As of 2010 the population was 718,451. The county seat is Redwood City. It is strongly Democratic, ethnically diverse, and affluent. The county’s built-up areas are mostly suburban with some areas being very urban, and are home to several corporate campuses.
San Mateo County straddles the San Francisco Peninsula, with the Santa Cruz Mountains running its entire length. The county encompasses a variety of habitats including estuarine, marine, oak woodland, redwood forest, coastal scrub and oak savannah. There are numerous species of wildlife present, especially along the San Francisco Bay estuarine shoreline, San Bruno Mountain, Fitzgerald Marine Reserve and the forests on the Montara Mountain block. Several creeks discharge to the San Francisco Bay including San Mateo Creek and Laurel Creek and several coastal streams discharge to the Pacific Ocean such as Frenchmans Creek and San Vicente Creek.