St. Martin Island Light is an exoskeleton lighthouse on St. Martin Island. It marks one of four passages between Lake Michigan and the bay of Green Bay. Constructed in 1905, this light tower is the only example in the US of a pure exoskeletal tower on the Great Lakes. Similar designs exist in Canada. Painted white, the hexagonal tower is made of iron plates which are supported by six exterior steel posts that have latticed buttresses. The cream city brick lightkeeper's house was modeled after that used for the Plum Island Range Lights.