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. Directly north of the Bronx are (from west to east) the adjoining Westchester County communities of Yonkers, Mount Vernon, Pelham Manor and New Rochelle. (There is also a short southern land boundary with Marble Hill in the Borough of Manhattan, over the filled-in former course of the Spuyten Duyvil Creek. Marble Hill's postal ZIP code, telephonic Area Code and fire service, however, are shared with the Bronx and not Manhattan.)

What's on the other side of the Hudson from the Bronx?