In a dramatic finish, returning champ Sammy Wanjiru of Kenya beat Tsegay Kebede of Ethiopia, champion of the London Marathon, to take the win.
He crossed the finish line at an unofficial time of 2:06:24. at a sprint, completing what was possibly the most exciting race of his life. As he crossed he waved and signaled to the crowd.
Kebede crossed at 2:06:43, followed by Feyisa Lilesa 2:08:10. The top American finisher was Jason Hartmann, who placed eighth and crossed at 2:11:06.
The win gives Wanjiru the lead in the World Marathon Majors. The purse for the Majors is $500,000. Kebede and Wanjiru had been tied at 50 points apiece going into the Chicago Marathon.
"Today was a very tough day," Wanjiru said. "We were fighting together. The problem was who was going to finish first."
Asked how he managed to find the last spurt of energy to sprint past Kebede, Wanjiru gave credit to the weather and to the crowds.
"This weather was my favorite weather," Wanjiru said. "American people are my favorite fans. Some say 'you can make it, you can make it.' I get the pleasure from the people who are watching, who are my fans."
For the women, Russia's Liliya Shobukhova also repeated. She broke away from the pack during the last five miles, and finished with an unofficial time of 2:20:25. The finish was her personal best time, beating her 2009 time of 2:25:56.
Finishing second was Ethiopia's Astede Baysa, with a time of 2:23:40. Third was Russia's Maria Konovalova, at 2:23:50. The USA's Desiree Davila placed fourth, at 2:26:20.
Shobukhova's time also breaks the Russian national record.
"I'm very happy right now," she said through a translator. "But I have a little bit more motivation to run faster."
Shobukhova said she loves the spectators in Chicago, and that their cheering gives her a lot of motivation. Shobukhova said her pace wasn't much affected by the heat.
"I don't know if I would have run much faster," she said through a translator. "But I would have drank much less water."