Most declined, but a few stopped for the treat.
One woman draped in a German banner stepped off the curb and sprinted alongside a racer to hand off a giant bottle of water.
Not far away, Urs Krieg and others were waving Swiss flags. Krieg, who lives near Zurich, was in town watching family members and friends race.
But had Krieg ever considered running?
"Maybe next year," he said with a laugh.
Near the starting line, friends and family were lined up on the sidelines cheering the runners on.
Julia Dragstrem of Naperville stood near Columbus Drive hoping to see her daughter-in-law pass through the start line.
"I think we could see her any second," she said, bouncing a homemade sign up and down. "Did we miss her?"
She had already missed her son, who was so engrossed in his headphones that he went right past.
"I had a big sign and everything," Julia said.
She is not a runner herself but says she is proud of her family.
"I think it's awesome to get out and do this."
Near North Avenue and LaSalle Drive, about 4.5 miles into the race, folks were cheering on the last group of runners to pass.
Patrick Little, 56, was holding up a sign that read, "E.T. Go Run Home" in support of his 54-year-old wife Elizabeth.
"We haven't seen her. She has got yellow flowers in her hair," he said, waving the sign above his head. "She has probably already passed."
Though she has been exercising for about five years, this was the first marathon for the Louisiana woman.
"I couldn't even do that," said her daughter Clara Little, 22. "I'm very impressed."
-- Mitchell Smith and Naomi Nix