The Bronx is the northernmost of New York City's five boroughs. The Bronx NY is the only borough situated primarily on the North American mainland (while the other four are on islands). The Bronx is almost entirely situated on the North American mainland. The Hudson River separates the Bronx on the west from Alpine, Tenafly and Englewood Cliffs in Bergen County, New Jersey; the Harlem River separates it from the island of Manhattan to the southwest; the East River separates it from Queens to the southeast; and, to the east, Long Island Sound separates it from Nassau County in western Long Island.