Brenna Dowell, who placed third in the all-around at the U.S National Championships, has been named the alternate.
The announcement was made on Saturday morning.
Biles is the 2013 U.S All-Around Champion and Ross finished in second. Ross was also on the 2012 gold medal winning U.S Olympic team.
With two strong all-around gymnasts, the announcement that Maroney will compete in the all-around is a surprise. She had originally been entered for only the vault and floor exercise competitions. Maroney, who was on the 2012 Olympic team with Ross, has been historically weak on balance beam and uneven bars but showed strong routines during training this week.
There has been mixed reaction to Karolyi’s decision to leave Dowell out of the competition that will start for the women on October 1. However, since 2001, Karolyi’s decisions have brought the United States’ women to great success including several World Championship and Olympic gold medals.