High Quality Content by WIKIPEDIA articles! Long Island Sound is an estuary of the Atlantic Ocean and numerous rivers located in the United States between Connecticut to the north and Long Island, New York to the south. The mouth of the Connecticut River at Old Saybrook, Connecticut, empties into the sound. On its western end the sound is bounded to the north by Westchester County, New York and the Bronx, and connects to the East River. On its eastern end it opens to Block Island Sound.