The Californian city on Earth that houses Starfleet Headquarters and Starfleet Academy, making it the place where many journeys begin and the target of more than one attack.
San Francisco is Starfleet's home. Headquarters and the Academy stand beside the Golden Gate Bridge, and the city appears in almost every series, from the launch of the NX-01 in Enterprise to the Academy scenes of The Next Generation and the Starfleet Academy series.
Time travel brings several crews to its past. Kirk's officers visit the city of 1986 in The Voyage Home, Data's head is found beneath it in Time's Arrow, and Sisko is caught up in the Bell Riots of 2024 in Past Tense.
The city is placed under martial law in Homefront and Paradise Lost, struck by the Breen in The Changing Face of Evil and attacked by Khan in the alternate reality of Star Trek Into Darkness.