Staten Island s a borough of New York City, coterminous with Richmond County, in the U.S. state of New York. Located in the southwest portion of the city, the borough is separated from New Jersey by the Arthur Kill and the Kill Van Kull and from the rest of New York by New York Bay. With an estimated population of 476,143 in 2019, Staten Island is the least-populated of the boroughs but is the third-largest in land area at 58.5 sq mi (152 km2). The borough also contains the southern-most point in the state, South Point. If each borough were ranked as a city, Staten Island would rank as the 39th most-populous in the U.S.