Wikipedia - World TeamTennis

World TeamTennis (WTT) is a mixed-gender professional tennis league played with a team format in the United States, which was founded in 1973.

The league's season normally takes place in the summer months. Players from the ATP and WTA take a break from their tour schedules to partake in World TeamTennis.

WTT was the first professional sports league to grant equal status to each man and woman competing for their teams.

Many top tennis players have participated in the league over the years, including Billy Jean King, Rod Laver, Björn Borg, Chris Evert, John McEnroe, Evonne Goolagong, Jimmy Connors, Martina Navratilova, Andre Agassi, Pete Sampras, Michael Chang, Serena Williams, Venus Williams, Lindsay Davenport, Kim Clijsters, Martina Hingis, John Isner, Sam Querrey, Sloane Stephens, Naomi Osaka, and Frances Tiafoe.