Organizers say the cool weather will provide ideal conditions for this year's race, which kicks off in Grant Park.
Meanwhile, Chicago's athletic elite are prepping for the marathon.
Henry Kozlowski, 62, has participated in the marathon every year since its inception in 1977.
"It gets to be a habit after a while. I started when I was younger and foolish and wanted to run a marathon," said Kozlowski.
The consultant from Wilmette, who is nearing retirement, is one of only nine runners who has completed every Chicago Marathon since1977.
He is joined by other marathon veterans, including Randy Burt.
"When we first started 45 years ago at the Daley Center… For many of us it was our first marathon and I don't think any of us knew we would be doing it this long," said Burt.
Burt, Kozlowski, and their peers will be at the start line one Sunday as the 35th running of the marathon steps off.
"It goes through all 29 different neighborhoods in Chicago over a 26 mile course. So it goes to the heart of the city," said Tim Maloney, president of the Bank of America Illinois.
Registration for the race closed in just 6 days- setting a record. Various factors drew in newcomers this year.
"I've heard about the course being easy, but also it's the history," said Stephanie Pezzullo, a first time marathon runner.
The competition pumped $219 million into the local economy last year.
"This is going to be a back to back sports weekend for the City of Chicago and back to back job creation for the City of Chicago," said Mayor Rahm Emanuel.
Although Lance Armstrong was banned from running amid steroid allegations, Chicagoans can still expect to see elite athletes like Russian Liliya Shobukhova, who could become the first runner to win four consecutive titles.
"I think she's going to turn that Olympic disappointment into history in Chicago… She's going to be tough to bet against," said Carey Pinkowski with the Bank of America Chicago Marathon.
Marathon organizers have decided to honor those who served in the military this year. The chief sponsor will donate $250,000 to the Wounded Warrior project.