Marin County /məˈrɪn/ is a county located in the San Francisco Bay Area of the U.S. state of California. As of the 2010 census, the population was 252,409. Its county seat is San Rafael. Marin County is included in the San Francisco-Oakland-Hayward, CA Metropolitan Statistical Area (San Francisco Bay Area) across the Golden Gate Bridge from San Francisco.
Marin County is well known for its natural beauty, liberal politics, and affluence. In May 2009, Marin County had the fifth highest income per capita in the United States at about $91,480. The county is governed by the Marin County Board of Supervisors.