Many more are turned away, but about a third of them got in by running for charity.
The runner spend months training for the day, putting in countless miles preparing to finish the marathon, 26.2 miles on the streets of Chicago.
They are among the fortunate ones who literally won the race lottery to get a bib. Organizers have to turn away at least as many as they are able to accept into the race.
"We are humbled by the demand and the support of the race," Executive Race Director Carey Pinkowski said.
As the race has grown dramatically since it started nearly a half century ago, the charity component has exploded. It's become a way to get into the race and make it more meaningful for many runners.
Jacob Fjare has type one diabetes, or T1D, and is raising money for research.
"It's like my personal experience so it's easier to dig in and ask people, 'Hey, I'd love for your support for this thing,'" Fjare said.
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Charity runners have become a big fundraising arm for the Breakthrough T1D organization.
"We've been a proud partner for over a decade," said Michael Mayberry with Breakthrough T1D Illinois. "In that time, our runners have raised more than $2.5 million."
Marathon partners with more than 200 charities raised more than $36 million last year alone.
In honor of the charity effort, Chicago artist Bob Faust created a piece depicting a marathon charity QR code displayed outside the Art Institute.
"It's really about giving back allowing a platform," said Rita Cook with Bank of America Illinois. "Everybody's running for something bigger than themselves."
The runners come to Chicago from every state and 14 different countries, but the money raised by the charity runners stays right in the city.