In 1973, the U.S. Open made history by offering equal prize money to men and women. Billie Jean King, the most visible advocate for the women's cause, earned over $100,000 in 1971 and 1972. In the famous Battle of the Sexes exhibition match against the vocally sexist Bobby Riggs in September 1973, King brought even more media attention to tennis, and to women professionals in all walks of life by beating Riggs. The Women's Tennis Association, formed in 1973, is the principal organizing body of women's professional tennis, organizing the worldwide, professional WTA Tour. From 1984–98, the finals matches of the championship event were best-of-five, uniquely among women's tournaments. In 1999, the finals reverted to best-of-three. The WTA Tour Championships are generally considered to be the women's fifth most prestigious event (after the four Grand Slam tournaments.) Sponsors have included Virginia Slims (1971–78), Avon (1979–82), Virginia Slims again (1983–94), J.P. Morgan Chase (1996–2000), Sanex (2001) Home Depot (2002), and Sony Ericsson (2006). In 1954, James Van Alen founded the International Tennis Hall of Fame, a non-profit museum in Newport, Rhode Island. The building contains a large collection of memorabilia as well as honoring prominent players and others. Each year, a grass-court tournament takes place on its grounds, as well as an induction ceremony honoring new members.