Margaret Osborne duPont was a female tennis player.
The Grand Slam tournaments , also called majors , are the four most-important annual tennis events . Margaret Osborne duPont ( born Margaret Evelyn Osborne ; March 4 , 1918 -- October 24 , 2012 ) was a World No. 1 American female tennis player . DuPont won a total of 37 singles , women 's doubles , and mixed doubles Grand Slam titles , which places her fourth on the all-time list despite never entering the Australian Championships . She won 25 of her Grand Slam titles at the U.S. Championships , which is an all-time record .