 It includes a number of properties previously listed on the National Register, including the former US Custom House (now a museum), the main post office, and the National Historic Landmark Caleb Cushing House.A particularly fine series of Federal mansions are to be found on High Street.It also has a substantial amount of residential architecture of the later 19th century, although this tends to be more vernacular in style, as it accompanied the rise of a lower industrial working class in the community.