Block Island is part of the U. S. state of Rhode Island and is located in the Atlantic Ocean approximately 13 miles (21 kilometers) south of the coast of Rhode Island, 14 miles (23 kilometers) east of Montauk Point on Long Island, and is separated from the Rhode Island mainland by Block Island Sound. The United States Census Bureau defines Block Island as Census Tract 415 of Washington County, Rhode Island. 734 square miles (25. 211 km2). The island is part of the Outer Lands region, a coastal archipelago made by the recessional and terminal moraine that resulted from the Wisconsonian Laurentide glacier retreat, about 22,000 years ago.