Washington Island is an uninhabited island in Lake Superior. It is within the boundary of Keweenaw County and Isle Royale National Park, a national park located within the U.S. state of Michigan. It is the westernmost point marked on most maps of the elongated archipelago that makes up this park. However, a small islet called Bottle Island and an even smaller shoal that breaks the lake surface, Rock of Ages, are located further westward.