Brooklyn is the most populous of the five boroughs of New York City, coextensive with Kings County, in the U.S. state of New York. Located at the westernmost end of Long Island and formerly an independent city, Brooklyn shares a land border with the borough and county of Queens. It has several bridge and tunnel connections to the borough of Manhattan, across the East River, including the architecturally significant Brooklyn Bridge, and is connected to Staten Island by the Verrazzano-Narrows Bridge.
The borough, as Kings County, at 37,339.9 inhabitants per square mile (14,417.0/km), is the second most densely populated county in the U.S. after Manhattan (New York County), and the most populous county in the state, as of 2022. In the 2020 United States census, the borough had a population of 2,736,074. Had Brooklyn remained an independent city on Long Island, it would now be the fourth most populous American city after the rest of New York City, Los Angeles, and Chicago. With a land area of 69.38 square miles (179.7 km) and a water area of 27.48 square miles (71.2 km), Kings County, one of the twelve original counties established under British rule in 1683 in the then-province of New York, is the state of New York's fourth-smallest county by land area and third smallest by total area.