William du Pont Jr. was an English-born American businessman and banker, and a prominent figure in the sport of Thoroughbred horse racing. He developed and designed more than 20 racing venues, including Fair Hill at his 5,000-acre estate in Maryland. A member of the Delaware Du Pont family, he was the son of William du Pont and Annie Rogers Zinn, and brother to Marion duPont Scott, a noted horsewoman and breeder.

Marion duPont Scott was a thoroughbred horsebreeder who operated a racing stable for both flat and steeplechase racing. She was the last private owner of Montpelier, the mansion and land estate of former United States President James Madison.