Is the East River, New York, A River or Long Island an Island?

The State of Rhode Island is disputing (United States versus Maine) the delineation of the closing line (a part of the baseline that crosses a body of water from which marginal seas are measured) separating the waters under Federal jurisdiction from State Waters in the vicinity of eastern Long Island Sound. Jurisdiction over some 595 km2 (172 nautical miles: ) of the continental shelf is in question. The United States legally considers Long Island Sound as historic inland waters. Rhode Island contends that Long Island is part of the mainland, thus moving the baseline seaward. The fundamental issue revolves around what constitutes the mainland, as determined by whether the East River is a river or a tidal strait. This paper examines the definitions of rivers and straits and develops working definitions for them. The physical characteristics of the East and Harlem Rivers are examined and compared with the working definitions as part of the litigation in this case.