Plum Island is an island at the western shore of Lake Michigan in the southern part of the town of Washington in Door County, in the U.S. state of Wisconsin. The uninhabited island has a land area of 1.179 square kilometres (0.455 sq mi) or 117.87 hectares (291.3 acres). The island is a bird sanctuary under control of the U.S. Coast Guard and will eventually become part of the Green Bay National Wildlife Refuge. The island also holds the unmanned Plum Island Range Lights.