At the place where the St. Mary’s River enters Lake Huron from Lake Superior, DeTour Passage separates the Upper Peninsula from Drummond Island and has long been a choke point for Great Lakes shipping. Anticipating increased traffic from the locks planned at Sault Ste. Marie, the U.S. Lighthouse Service built an onshore light station on Point DeTour in 1848. As vessels grew in size, DeTour Reef, extending a mile from Point DeTour in twenty feet of water, became a greater hazard, and in 1929 the Lighthouse Service decided to replace the onshore light with a station atop the reef. Located four miles southeast, the DeTour Reef Light Station was constructed by the U.S. Army Corps of Engineers in 1931 and is one of only six reef light stations in Michigan. The 1861 tower, Fresnel lens, and lantern assembly were moved from the Point DeTour Light Station. The new station housed resident keepers, equipment, and supplies in three stories, and its tower rises more than eighty feet above the water atop a forty-one-foot-high wood crib and concrete pier resting on DeTour Reef. The Coast Guard automated the station in 1974 and excessed it in 1997. The DeTour Reef Light Preservation Society, established in 1998, restored the station in 2004, opened it to visitors in 2005, and took ownership in 2010.