Gilder died suddenly in New York City on Friday 19 November 1909 of a heart attack in the home of Schuyler van Rensselaer(at 9 West 10th St). The cause of death is considered to be heart disease.He had been staying at the Rensselaer home as a guest for several days (since the previous Monday, 15 November 1909) with his wife (Helena) when he suddenly died.He had been ill two weeks prior to his death, while he had been giving a lecture, but the incident was not considered to be serious at the time.Gilder is buried at the Bordentown Cemetery in Bordentown New Jersey.