Reigning Olympic champions Sydney McLaughlin and Athing Mu won titles and two-time Olympian turned NFL receiver Devon Allen set a meet record on Saturday at the Penn Relays.
Tokyo Olympic 400-meter hurdles champion McLaughlin won the 100 hurdles in a meet-record 12.75 seconds while 19-year-old US compatriot Mu, the 800m winner in Tokyo, took the seldom-contested 600m in 1:22.74 at Philadelphia's Franklin Field.
Allen, who signed a deal with the NFL's Philadelphia Eagles earlier this month, beat former world and Olympic champion Omar McLeod of Jamaica to win the men's 110 hurdles.
McLaughlin was pleased with her return to competition, defeating Canadian runner-up Mariam Abdul-Rashid by .42 of a second.
"I was really excited to come back," McLaughlin said. "I just wanted to start my season off strong and gauge where I was at."
It was much the same for Mu, who was making her season debut as athletes prepare for July's world championships in Eugene, Oregon.
"We're all just out here getting ready to compete for the world championships," she said. "Being in Eugene is going to be a great time."
With 100m to go, Mu surged ahead of Ajee Wilson, this year's world 800m indoor champion and a two-time world 800m podium finisher, to win by 1.35 seconds over Jamaican runner-up Natoya Goule with Wilson fading to sixth in 1:25.87.
"It's terrible in workouts but it's fun out here when you have competition," Mu said of the 600. "It's a good day."
Allen, an American with top-five finishes at the past two Olympics but no medal, won in 13.11 seconds to beat 2016 Olympic champion and 2017 world champion McLeod by .11sec.
"I was excited," said Allen, who spent the week training with the Eagles. "You know it's a good day to come out and beat Omar, one of the best in the world."
Britain's Callum Elson won the men's mile in 4:04.11, defeating Kenyan Festus Lagat by .20sec, and American Anna Camp Bennett took the women's 1,500m in 4:09.54.
Ghana's Alex Amankwah won the men's 600 in 1:15.88 with Jamaica's Rajay Hamilton second in 1:16.00.
"We were just trying to have fun," Amankwah said. "We were just chilling."
Philadelphia-born Nigerian standout Chidi Okezie won the men's 300 in 32.68 seconds, edging Jamaican Rusheen McDonald by .01sec at the line.
"You can run it all out. That was the game plan," Okezie said. "I knew I had to give it all I had."
American Anavia Battle won the women's 300 in 36.70 less than an hour after taking the 100m college title for Ohio State with Britain's Nicole Yeargin second in 37.15.