Margaret Osborne duPont was already a tennis champion when she married William duPont, Jr. in 1947, and she went on to win titles in the United States and Europe while also advancing tennis in Delaware. A regular on the public courts of her hometown of Joseph, Oregon, she won her first trophy at age 12 in 1930 after her family moved to San Francisco, entered the California State Tournament in 1931, and won her first national championship in 1936. She became one of women's tennis's greatest players, earning 25 U.S. titles, seven wins at Wimbledon, England, and five at the French Championships. She was inducted into the International Tennis Hall of Fame in 1987 and the Delaware Sports Hall of Fame in 1996. After her marriage, she and William duPont, Jr. promoted tennis in Delaware, where she served as an officer of the Delaware Lawn Tennis Association, helped build sixty public tennis courts, sponsored young players throughout the state, and helped secure financial support from the United States Lawn Tennis Association, a distinction otherwise shared only by New York. In 1964, she moved to Texas to breed and race thoroughbred horses with her friend and former racquet sports star Margaret Verner Bloss.