San Francisco owns SFO though the airport sits in San Mateo County

San Francisco International Airport is owned and operated by the City and County of San Francisco but the airport's airfield and terminals are physically located in unincorporated San Mateo County near the cities of Millbrae and San Bruno. The airport uses San Francisco postal codes (94128) and the San Francisco Airport Commission governs operations, creating a long-standing jurisdictional oddity between the two counties. This arrangement dates to the airport's development and subsequent governance decisions by the city.