In 1953, she married her third and final husband, Vincent Astor (1891-1959), the chairman of the board of Newsweek magazine and the last notably rich American member of the famous Astor family. The oldest son of Titanic victim John Jacob Astor IV (1864-1912) and his first wife, Ava Lowle Willing, he had been married and divorced twice before and was known to have a difficult personality.
During her brief marriage to Astor, whom she called "Captain," Astor participated in his real-estate and hotel empire and his philanthropic endeavors. Between 1954 and 1958, she redecorated one of his properties, the Hotel St. Regis, which had been built by his father.
Despite receiving several proposals after Astor's death, she chose not to remarry. "I'd have to marry a man of a suitable age and somebody who was a somebody, and that's not easy. Frankly, I think I'm unmarriageable now," Astor said in an interview in 1980, when she was 78. "I'm too used to having things my way. But I still enjoy a flirt now and then."
Though she was appointed a member of the board of the Astor Foundation soon after her marriage, upon Vincent Astor's death in 1959, she took charge of all the philanthropies to which he left his fortune. Despite liquidating the Vincent Astor Foundation in 1997, she continued to be active in charities and in New York's social life. The New York Public Library was always one of Astor's favorite charities. As a result of her charity work, Astor was awarded the Presidential Medal of Freedom in 1998. Her life's motto summed up her prodigious generosity: “Money is like manure; it’s not worth a thing unless it’s spread around.”
Among numerous other organizations, she was involved with Lighthouse for the Blind, the Maternity Center Association, the Astor Home for emotionally disturbed children, the International Rescue Committee, the Fresh Air Fund, and the Women's Auxiliary Board of the Society of New York Hospital.
Astor died on August 13, 2007 at the age of 105 from pneumonia at her home in Briarcliff Manor, New York. She is interred in Sleepy Hollow Cemetery, Sleepy Hollow, New York. The epitaph on her gravestone, chosen by her, simply reads: "I had a wonderful life".
November 27, 2007 - At age 104, Astor's son, Anthony Marshall, was indicted on charges of grand larceny, criminal possession of stolen property, forgery, scheming to defraud, falsifying business records, offering a false instrument for filing, and conspiracy in plundering her $198 million estate.