State Senate District 3 includes the entire Counties of Napa, Solano, Yolo, and portions of Contra Costa, Sacramento, and Sonoma Counties. It also includes the whole Cities of American Canyon, Benicia, Brentwood, Calistoga, Cotati, Davis, Dixon, Fairfield, Isleton, Napa, Oakley, Rio Vista, Rohnert Park, St. Helena, Sonoma, Suisun City, Vacaville, Vallejo, West Sacramento, Winters, Woodland, and Yountville.