There are nine NHL ships, including a warship and a tugboat that served in World War II, one warship that saw combat in the Vietnam War, three sailing boats, two fireboats and a lightvessel. Salient in the list are 24 mansions, and four sites primarily significant for their architectural landscaping. Many properties, numbering in the thousands, are contributing or non-contributing structures in the state's nine National Historic Landmark Districts. Intellectual accomplishments of New Yorkers are associated with 22 sites, including nine university buildings, ten other NHLs associated with inventions, inventors or scientists, and four engineering landmarks, including two bridges that were once the longest of their types. Commercial accomplishments include 11 historic skyscrapers, five of which were once the tallest in the world, seven stock exchanges and other buildings important in commercial history, two bank buildings, five industrial facilities, and three water-based civil engineering works. Two are architectural oddities. Political and social accomplishments are represented by four former mental care institutions (a legacy of the state's leading role in mental health care), 14 sites associated with suffragettes or other women leaders, five Underground Railroad or other sites associated with abolitionists, six sites associated with African-American leaders, three sites associated with labor rights, and four sites associated with other social activism. In addition, there are 21 homes of other national leaders, and six government buildings that are significant on a national scale. Community, arts and entertainment accomplishments represented include two utopian communes, the Adirondack Park and four of its Great Camps, and five other retreat sites. No fewer than nine artist homes or studios are landmarked, as well as nine homes of writers and composers. There are four club buildings, of which two are historical societies, and eight entertainment venues or sites associated with entertainers. Sixteen others are unique sites that are difficult to classify. Notable architects whose work is represented in the NHLs of the state include: Alexander Jackson Davis (7 sites), Andrew Jackson Downing (2), William West Durant (2), Leopold Eidlitz (2), Cass Gilbert (2), Henry J. Hardenbergh (2), Raymond Hood (3), Philip Hooker (2), Minard Lafever (7), John McComb Jr. (3), Frederick Law Olmsted (3), Isaac G. Perry (2), George B. Post (3), James Renwick, Jr. (4), Henry Hobson Richardson (2), Louis Sullivan (2), Richard Upjohn (6), Calvert Vaux (6), and Frederick Clarke Withers (2).