Oakland was a city located in the San Francisco Metropolitan Area, California.
In 1941, a poster for boxing listed matches in this city. The headline match was between DeWaay and Johnson. (TNG: "The Big Goodbye")
In 1986, its location was labeled on a San Francisco Municipal Railway system map. In the late 20th century, Oakland was the site of two military bases: the Oakland Army Base and the Oakland Supply Depot. This city was connected to San Francisco by the San Francisco-Oakland Bay Bridge. (Star Trek IV: The Voyage Home)
In 2151, an artist in Oakland was awaiting a decent photograph of Captain Jonathan Archer in order to paint Archer's portrait, which would in turn be hung on the wall in Starfleet Command in the captain's honor. (ENT: "Rogue Planet")
It was not established which Oakland the artist resided in, though Oakland, California is the largest city with that name, and also close to Starfleet Command in San Francisco.
In an alternate 2404, Admiral Kathryn Janeway appropriated SC-4 from the Oakland Shipyard. (VOY: "Endgame")