San Francisco, officially the City and County of San Francisco, is 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 884,363 residents as of 2017. 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.