Block Island is an island in the Atlantic Ocean approximately twelve miles south of the coast of Rhode Island. It is separated from the 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 2000 census it had a population of 1,010 living on a land area of 25.211 kmĀ² (9.734 sq mi). The island is a fragment of glacial terminal moraine (tracing through the Outer Lands region).