Eldridge, making her third appearance at the NCAA meet, clocked a 1:09.43 in the finals after a 1:09.08 finish in the morning prelims.
"I was excited about my swim," Eldridge commented after boosting WSU into 28th in team scoring. "I hope it carries over into tomorrow in the 200. It is one of the few time I have been pleased with my performance at a big meet."
Last year she earned All-America honors with a 13th place finish over 100 meters and as a sophomore she finished 23rd in the 100 breaststroke.
"Erin swam against several Gold medalists from the recent Olympics, Pan Pacifics and Wold University Games, so I am pleased to see her swim against that elite level of competition," Cougar swim coach Rocco Aceto said. "I am excited about the future of Cougar swimming because Erin has opened the door on the highest level."
Eldridge, the only Cougar women to ever compete in the NCAA meet, will swim the 200 meter breaststroke Saturday. In 1998 she finished 26th in the 200 event, then came back last year to finish 13th.
Georgia senior Kristy Kowal won the compeition Friday with an American record 1:05.74. Kowal also broke Arizona freshman Amanda Beard's American record in the morning prelims. Beard finished fourth in the competition.