San Francisco is in the United States.
California ( [ kælᵻˈfɔːrnjə , _ - ni.ə ] , ) is the most populous state in the United States and the third most extensive by area . Craigslist ( stylized as craigslist ) is an American classified advertisements website with sections devoted to jobs , housing , personals , for sale , items wanted , services , community , gigs , résumés , and discussion forums . The Panama -- Pacific International Exposition ( PPIE ) was a world 's fair held in San Francisco , in the United States , between February 20 and December 4 in 1915 . San Francisco . Located at the north end of the San Francisco Peninsula , San Francisco is about 47.9 sqmi in area , making it the smallest county -- and the only consolidated city-county -- within the state of California . San Francisco is the fourth-most populous city in California , after Los Angeles , San Diego , and San Jose , and the 13th-most populous city in the United States -- with a census-estimated 2016 population of 870,887 .