The Lowell Historic Preservation District is a historic district created by the legislation establishing Lowell National Historic Park. The district encompasses an area of more than 500 acres (200 ha), including virtually all of the historically significant resources associated with the industrial history of the city of Lowell, Massachusetts. It includes the industrial mill complexes, worker housing areas, central business district, and civic heart of the city, as well as the water power infrastructure that powered the mills.