sentences:  By 1925 nearly all of the Great Lakes lighthouses that exist today had been constructed, except for Poe Reef Light, Gravelly Shoal Light, and Manning Memorial Light.Another is the William Livingtone Memorial Light, and the Great Lakes light, namely Tri-Centennial Light of Detroit.This is part of a larger pattern of building 14 reef lights around Michigan, which was intended to help ships navigate through and around the shoals and hazards around the Straits of Mackinac.