Olmsted Island is a small island in the middle of the Potomac River in the U.S. state of Maryland, near Great Falls which is a part of C & O Canal National Historical Park, located across the river from Great Falls Park. It is a part of Potomac, Maryland.Named for Frederick Law Olmsted, Jr., the landscape architect and preservationist whose famous father designed New York's Central Park, the small island is a bedrock terrace forest that supports rare, threatened and endangered plant species.