He told her that he received "thousands of letters" from women offering to marry him and that "a secretary had been appointed to take charge of this class of mail." Green told Martyn: "Why, it isn't my "money" they want to marry me for. It's "alimony."" As Hetty strongly opposed his marrying, he waited until after her death in 1916 to wed his longtime companion, Mabel E. Harlow, a former prostitute. He and his sister Sylvia each inherited half of their mother's fortune of $150 million or more. In addition to the various other homes he already owned, after his mother's death, Green built a mansion in Massachusetts, Round Hill, and another on Star Island. The Round Hill mansion was designed by the Anglo-American architect Alfred C. Bossom and completed in 1921 at a cost of $1.5 million. He died of heart disease at Lake Placid, New York, in 1936. In accordance with Green's last request, his widow had his amputated leg exhumed and reunited with the rest of his body. His widow and his sister fought over his estate, estimated at the time as $44,384,500 or "more than $40 million". Green had persuaded Mabel to sign a prenuptial agreement, which limited her to a $1,500 monthly stipend, but she challenged it in court. She eventually settled for $500,000. Four states, Texas, Massachusetts, Florida and New York, fought over who would collect $6 million in inheritance taxes. The United States Supreme Court awarded the money to Massachusetts. Green is known to philatelists for forming one of the great collections of postage stamps of the early 20th century, exceeded in size and value only by that of King George V. In 1918, he purchased the sheet of Inverted Jenny stamps from the dealer Eugene Klein for $20,000. On Klein's advice, he broke the sheet up into blocks. He put one stamp in a locket he gave to his wife. To numismatists, Green is known for his extensive coin collection. Most notably, he was one of the original owners of all five of the 1913 Liberty Head Nickels known to exist. He brought one of the first automobiles into Texas, "a two-cylinder St. Louis Gas Car surrey, designed by George Norris ["sic" - the correct name is Dorris]", and is reputed to have been involved in the first car accident in the state, when the car was forced off the road into a ditch by a farm wagon in October 1899 in Forney, Texas.