Plum Island Lighthouse

Porte des Morts, or Death’s Door, is a narrow strait separating the tip of Door County Peninsula from a collection of islands that extends north to Michigan’s upper peninsula. These islands, which include Plum Island, Detroit Island, Washington Island, Rock Island, St. Martin Island, Summer Island, and Poverty Island, form a dividing line between Green Bay and Lake Michigan, and in 1837 a lighthouse, the first on Lake Michigan, was built on Rock Island to guide vessels through Rock Island Passage. This northern passage was convenient for vessels traveling between the Straits of Mackinac and Green Bay, but as Milwaukee and Chicago grew in importance, traffic from these ports preferred taking the more southerly Death’s Door Passage to Green Bay, as it saved significant time.