AC Transit (Alameda-Contra Costa Transit District) is an Oakland-based public transit agency serving the western portions of Alameda and Contra Costa counties in the East Bay portion of the San Francisco Bay Area. AC Transit also operates "Transbay" routes across San Francisco Bay to San Francisco and selected areas in San Mateo and Santa Clara counties. AC Transit is constituted as a special district under California law. It is governed by seven elected members (five from geographic wards and two at large). It is not a part of or under the control of Alameda or Contra Costa counties or any local jurisdictions.