complex, although its interior has been modernized and converted to office and administrative uses by the Smithsonian. See also List of Gilded Age mansions National Register of Historic Places listings in Manhattan from 59th to 110th Streets List of National Historic Landmarks in New York City References Further reading Ewing, Heather. (2014). Life of a Mansion: The Story of Cooper Hewitt, Smithsonian Design Museum. Cooper Hewitt, Smithsonian Design Museum, New York. External links Cooper Hewitt, National Design Museum Andrew Carnegie Babb, Cook and Willard buildings Fifth Avenue Houses completed in 1903 Houses in Manhattan Houses on the National Register of Historic Places in Manhattan National Historic Landmarks in Manhattan New York City Designated Landmarks in Manhattan Upper East Side Gilded Age mansions 1903 establishments in New York City