Mary Lillian Duke Biddle was an American philanthropist.

The Benjamin N. Duke House, also the Duke–Semans Mansion and the Benjamin N. and Sarah Duke House, is a mansion at 1009 Fifth Avenue, at the southeast corner with 82nd Street, on the Upper East Side of Manhattan in New York City. It was built between 1899 and 1901 and was designed by the firm of Welch, Smith & Provot. The house, along with three other mansions on the same block, was built speculatively by developers William W. Hall and Thomas M. Hall. The Benjamin N. Duke House is one of a few remaining private mansions along Fifth Avenue. It is a New York City designated landmark and is listed on the National Register of Historic Places.