Dalton Rowan threw the discus 189 feet, 1 inch (57.65) to advance to Thursday's final, which will start at 7:55 p.m. in Spain and 12:55 p.m. local time.
While Rowan's mark ranked eighth among the 12 throwers who made the final, he finished fourth among the second group of 14 throwers with a series of three throws that included an opening round toss of 185-3 (56.48), then a 182-0 (55.48) before hitting his best mark in the third round.
Poland's Wojciech Praczyk led the discus field with a toss of (60.72) while Rowan's US teammate Rodney Brown of LSU placed 18th in qualifying with a mark of 179-4 (54.66).
In the men's 400, Aldrich Bailey was a heat winner with a time of 46.40 while U.S. teammate Arman Hall led all qualifiers with a 46.13 clocking. Bailey made a 46.40 look exceedingly easy in taking his heat by three-tenths of a second.
"The race was just an opener," said Bailey. "I didn't want to do anything too special. (The Olympic Trials) gave me a lot of good experience, teaching me the way to run rounds the correct way and save as much as possible for the last one. Overall, today was okay - nothing too special."
In the women's 100 meters, reigning World Youth Champion Jennifer Madu won her heat in 11.64 into a steady headwind (-2.6), but noted there's more to improve on.
"I wanted to come out and get my legs running again," said Madu. "Maintaining speed is something I'm good at, but my start has been off-and-on. I just hope I can come back next round and take care of business."
Madu will have to contest a pair of 100m races, a semifinal and final, on Wednesday after starting out the day with triple jump qualifying. Bailey, meanwhile, competes in the semifinal of the 400.