When the open era began, King campaigned for equal prize money in the men's and women's games. In 1971, her husband, Larry King created the idea to form a nine player women's group with the financial backing of "World Tennis" magazine founder Gladys Heldman and the sponsorship of Virginia Slims chairman Joe Cullman. King became the first woman athlete to earn over US$100,000 in prize money; however, inequalities continued. King won the US Open in 1972 but received US$15,000 less than the men's champion Ilie Năstase. She stated that she would not play the next year if the prize money was not equal. In 1973, the US Open became the first major tournament to offer equal prize money for men and women.