Long Island is a densely populated island in the southeast part of the U.S. state of New York, in the northeastern United States. At New York Harbor, it is approximately 0.35 miles (0.56 km) from Manhattan Island and extends eastward over 100 miles (160 km) into the Atlantic Ocean. The island comprises four counties; Kings and Queens counties (the New York City boroughs of Brooklyn and Queens, respectively) and Nassau County share the western third of the island, while Suffolk County occupies the eastern two thirds. More than half of New York City’s residents live on Long Island, in Brooklyn and in Queens. However, people in the New York metropolitan area colloquially use the term Long Island (or the Island) to refer exclusively to Nassau and Suffolk counties, and conversely, employ the term the City to mean Manhattan alone. While the Nassau-plus-Suffolk definition of Long Island does not have any legal existence, it is recognized as a “region” by the state of New York.
Broadly speaking, “Long Island” may refer both to the main island and the surrounding outer barrier islands. To its west, Long Island is separated from Manhattan and the Bronx by the East River tidal estuary. North of the island is Long Island Sound, across which lie Westchester County, New York and the state of Connecticut. Across the Block Island Sound to the northeast is the state of Rhode Island. Block Island—which is part of Rhode Island—and numerous smaller islands extend further into the Atlantic. To the extreme southwest, Long Island is separated from Staten Island and the state of New Jersey by Upper New York Bay, the Narrows, and Lower New York Bay.