His then burst to the lead in the final miles for a victory of 2 hours 9 minutes and 20 seconds. His win punctuated a resurgent day for American marathoning.
Rupp was the first American winner in the Chicago Marathon since Khalid Khannouchi in 2002 and the first American-born male winner since Greg Meyer in 1982. In the women's race, Jordan Hasay finished third in 2:20:57, recording the second-fastest time ever for an American woman and breaking Joan Benoit Samuelson's 1985 course record for an American woman.
"It's tremendous," Rupp, whose father, Greg, is from Maywood, said. "It's fun to be part of it. It's fun to see Americans competing on the international level. It's real fun to see American doing well again. Hopefully we can inspire a future generation."
Rupp's moment has been coming, rising from the track to the road. He made his marathon debut in 2016 by winning the U.S. Olympic Marathon trials, placed second at the Boston Marathon and earned a bronze medal in Rio de Janeiro.
Hasay similarly has transitioned from track to marathons. In April, she recorded the fastest debut ever by an American woman for a fourth-place finish at the Boston Marathon.
When she crossed the finish line, she said she immediately asked how Rupp — with whom she sometimes trains in Portland — did.
"That's one of the reasons that I went with that lead pack today," said Hasay, who was met at the finish by Samuelson. "It's important to show we can compete with them. That's one of the things I was telling myself, 'Be confident. You can compete with these ladies.'"
Rupp and Hasay's performances mark a pivotal moment for American marathon running and could spark future generations of elite distance runners.
"I think this was a really inspiring day for the sport in America," said Deena Kastor, an American who earned a bronze in the 2004 Olympics marathon. "This was a star-studded field. It wasn't buffered down. There were world record holders, Olympic medalists, previous champions. … Growing up you just heard, the East Africans are so dominant. If you believed in that story, you fell in line. "
She said more Americans are making the podium at track distance events and Americans runners are entering the marathon younger. Hasay, 26, and Rupp, 31, both said they plan to focus on marathon running now rather than the track, where each is accomplished.
"Marathon running is something (American) distance runners would try when they started to lose their track speed," Kastor said. "Now you see people with promise getting in at the height of their career rather than the end of it."
Rupp broke out of a relatively slow group of runners, calling on his track background to record mile splits of 4:39, 4:35 and 4:31 between Miles 21-23. Defending champion Abel Kirui finished second in 2:09:48, and fellow Kenyan Bernard Kipyego finished third in 2:10:23.
"It was real important for me to sit back and relax and conserve energy," he said. "That was my mantra. When it was time to go I wanted to make a real decisive move. At that point, you have to be all in."
Hasay kept with a fast, aggressive pace for much of the race before Tirunesh Dibaba (Ethiopia) broke free from the pack with second-place finisher Brigid Kosgei (Kenya).
"I had to definitely be very brave," Hasay said. "I was little indecisive. Do I go? Do I not go? I had to be really tough and stick to my rhythm that second half. I'm just thankful that training really carried me though."
Two-time defending champion Florence Kiplagat, from Kenya, did not finish the race, dropping out at the 25 kilometer mark. Dennis Kimetto, who holds the world record, dropped out of the men's race as well after starting to limp at Mile 14.
More than 43,000 runners participated in Sunday's race.