Long Island Sound is a tidal estuary of the Atlantic Ocean, lying between the eastern shore of Bronx County, New York City, the southern shores of Westchester County and Connecticut, and the northern shore of Long Island. The sound stretches 110 miles (177 km) from the East River in New York City eastward along the north shore of Long Island to  Block Island Sound. A mix of freshwater from tributaries and saltwater from the ocean, Long Island Sound is 21 miles (34 km) at its widest point and varies in depth from .