Grays Reef Light is an offshore lighthouse in northeastern Lake Michigan near the Straits of Mackinac, built to mark the dangerous shoals at Grays Reef as iron ore traffic increased in the late 19th century. Before the permanent station, a series of lightships served the reef from 1891 until underwater construction made a fixed lighthouse feasible. Congress funded the present structure in 1934, and it was completed in September 1936. Control passed to the United States Coast Guard in 1939, and staffing ended in 1976. Its reinforced-concrete pier, steel-clad tower, and durable design made it a notable example of Great Lakes offshore engineering.