Gauff, the 15-year-old based in Florida who announced herself to the world at Wimbledon, and McNally, a 17-year-old from Ohio, were granted a doubles wild card by the U.S. Tennis Association on Saturday.
Each previously was given a wild card for the singles main draw, too. The tournament begins Monday.
A year ago, Gauff and McNally won a US Open junior title in doubles. They then picked up the first WTA trophy for each by winning the doubles title at the Citi Open in Washington this month.
McNally also reached her first tour-level semifinal in singles at that hard-court tournament.
Gauff's big breakthrough in singles came at the All England Club this year. She became the youngest qualifier in Wimbledon history, then beat Venus Williams in the first round and made it to the fourth round before losing to eventual champion Simona Halep.