California is a region of the North American continent and a state in the former nation-state, the United States of America, on Earth. It borders the Pacific Ocean on its western side.
Cities in California include Los Angeles, San Francisco, San Diego and Anaheim. Mill Valley is a small city, fourteen miles north of San Francisco, where the 602 Club is located.
Various Starfleet facilities, including Starfleet Command and Starfleet Academy, were located in and around San Francisco, California.
The Exobiological Research Laboratory was located in Encino, California. (VOY: "Dark Realm")
Disneyland, located in Anaheim, was apparently still in existence 339 years after it was first opened. Peter Kirk took Leonard McCoy and his two sons there. (Orion Press: "Incident")
Sanctuary Districts were located in various cities in the US by 2024. The famous Bell Riots occurred in San Francisco when the Californian governor ordered troops to take the facility back by force, resulting in hundreds of deaths. (DS9: "Past Tense, Part I", "Past Tense, Part II")
In 2047, the Hermosa Earthquake saw a large part of the Californian coast sink into the Pacific Ocean. (VOY: "Future's End")
The California-class starships of the late 24th century were named after this state. All of the ships of this class are named after municipalities within the state. (Star Trek: Lower Decks)