New Zealand's Geordie Beamish, last year's world indoor 1 500m champion, charged late on the outside to win the Penn Relays men's mile in 3mins 56.85 on Saturday.
In wet conditions at Philadelphia's Franklin Field, Beamish edged US runner-up Sam Ellis by .03 of a second with American Wes Porter third, .07 adrift, in the 129th edition of the famed American meet.
Elite events were used by many as an early tune-up for September's World Athletics Championships in Tokyo.
"It was a lot of fun," Beamish said. "Really happy to be back on the track.
"It was a tough last 150 to finish. That finish line comes up real quick and I almost got it wrong but it's so much fun to get it right."
American Josette Andrews won the women's 1 500m in a meet record 4:01.76 to open her outdoor season.
American Dani Jones was second in 4:03.21 with Japan's Nozomi Tanaka third in 4:05.44.
"I was feeling really good so not wanting to leave anything to chance and just push it," Andrews said.
Robert Farken, the 2022 German champion, won the 800 in 1:45.45, 0.31 of a second ahead of American Shane Cohen.
"My first time racing here. I only heard the stories about it and it definitely didn't disappoint," Farken said. "Even though the weather isn't great, the crowd is even better."
Two-time reigning US champion Nia Akins won the women's 800 in 2:00.49 in her outdoor season opener with France's Cindy Bourdier second in 2:02.80.
Jamaica's Shanieka Ricketts, last year's Paris Olympic runner-up and a two-time world runner-up, won the women's triple jump with a leap of 14.17m while compatriot Imani Oliver was second on 13.54.
Jah-Nhai Perinchief of Bermuda won the men's triple jump by clearing 16.86m with Kaiwan Culmer of Bahamas second on 16.41.
American Bailey Lear won the women's 400 in 51.21 seconds with Jamaica's Leah Anderson second, 1.08 seconds back.
Samantha Watson won the women's 600 in 1:28.30, beating US compatriot Sarah Jane Underwood by 0.56 of a second, while American Will Sumner captured the men's 600 in 1:17.36 with Jonathan Jones of Barbados second in 1:18.33.