San Francisco (SF; /ˌsæn frənˈsɪskoʊ, fræn-/, Spanish: [sam fɾanˈsisko]; Spanish for 'Saint Francis'), officially the City and County of San Francisco, is a city in, and the cultural, commercial, and financial center of, Northern California. San Francisco is the 13th-most populous city in the United States, and the fourth-most populous in California, with 883,305 residents as of 2018. It covers an area of about 46. 89 square miles (121. 4 km2), mostly at the north end of the San Francisco Peninsula in the San Francisco Bay Area, making it the second-most densely populated large US city, and the fifth-most densely populated U. S. county, behind only four of the five New York City boroughs. San Francisco is also part of the fifth-most populous primary statistical area in the United States, the San Jose–San Francisco–Oakland, CA Combined Statistical Area (9. 67 million residents).