Last year's World championships finalist Emma Coburn clocked 9:17.48 to win her second US steeplechase title and to book her ticket to Rio Olympics on Thursday night. Courtney Frerichs and Colleen Quigley also made the US Olympic team after they crossed the line in second and third respectively.
In the men's 200m qualifying rounds with no big difficulties favourites Justin Gatlin, LaShawn Merritt, Tyson Gay and Ameer Webb qualified for Friday's semifinals.
Elsewhere, World indoor champion Michelle Carter topped the women's shot put final in a new season's best of 19.59. Meanwhile Raven Sounders took silver with a toss of 19.24m just 1cm ahead of Felisha Johnson, who placed in third place.
Keturah Orji prevailed in the women's triple jump final with a leap of 14.32m followed by Christina Epps (14.17m) and Andrea Geubelle (13.95m).