Townsend is an 18-year-old from Chicago who is a former junior No. 1 and reached the third round at the French Open this year. Min won the 2011 US Open girls' title, while Gibbs and Collins are NCAA champions.
Other wild-card entries announced Tuesday by the U.S. Tennis Association are past Wimbledon and Australian Open junior finalist Madison Brengle, USTA girls' national champion CiCi Bellis, Australia's Jarmila Gajdosova and France's Amandine Hesse.
The US Open, the year's last Grand Slam tournament, starts Aug. 25.