The Coolidges had two sons: John (September 7, 1906 – May 31, 2000) and Calvin Jr. (April 13, 1908 – July 7, 1924). Calvin Jr. died at age 16 from blood poisoning. On June 30, 1924 Calvin Jr. had played tennis with his brother on the White House tennis courts without putting on socks and developed a blister on one of his toes. The blister subsequently degenerated into sepsis and Calvin Jr. died a little over a week later. The President never forgave himself for Calvin Jr's death. His eldest John said it "hurt terribly." John became a railroad executive, helped to start the Coolidge Foundation, and was instrumental in creating the President Calvin Coolidge State Historic Site.