Block Island is part of the U.S. state of Rhode Island. It is located in the Atlantic Ocean about 13 miles (21 km) south of the coast of Rhode Island, 14 miles (23 km) 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. As of the 2010 census the population of 1,051 lived on a land area of 9.734 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.