The Nantucket Historic District is a National Historic Landmark District that encompasses the entire island of Nantucket, Massachusetts. The original December 13, 1966 listing on the National Register of Historic Places included only the historic downtown core and the village of Siasconset, but was expanded in 1975 to include the entire island, as well as the islands of Tuckernuck and Muskeget. At over 30,000 acres, it is the largest conventional historic National Historic Landmark District by area in the contiguous United States.