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.