Statement of Significance (as of designation - November 13, 1966):
Andrew Carnegie, who arrived in the United States from Scotland at age 13, became a steel industrialist and philanthropist, and one of the nation's richest men. His empire included coal mines, steel mills and steamship and rail lines. He had this 64-room brick mansion, which he intended to be "the most modest, plainest and roomiest house in New York," built after his retirement in 1901. From the house he devoted the rest of his life to philanthropy, in particular the establishment of public libraries across the nation.