In 1939, Isabella married her third husband Harry Orland King, a New York industrialist whom she had worked with while in Congress. During the next decade she divided her time between homes in New York City, Washington, D.C., and Tucson carrying on her philanthropies and volunteer services.

Isabella Selmes Ferguson Greenway King died in December 1953 after a series of heart attacks. Having inherited the Dinsmore farm in 1926 after the death of her great aunt Julia, the homestead would