The Bank of America Chicago Marathon began accepting registrants at 12 p.m. Wednesday.
Last year, the website crashed shortly after runners began signing up, so Chicago Marathon organizers said they switched their registration to a lottery system for the first time.
Runners will be guaranteed one of the 45,000 spots if they have participated in five of the last 10 years or meet certain time requirements: 3 hour 15 minute for men, 3 hour 45 minutes for women. A lottery will be held for non-guaranteed spots.
Mark Rentfro entered the lottery. He's never run a 26.2 mile course in Chicago, and he'll need a little luck to get the chance this year.
"Everything I've heard about it, it's very well supported, people line the streets, always did kind of feel like the people's marathon," Rentfro said.
Kristin Kosta isn't taking her chances with the lottery.
"I plan on running it until I can no longer run anymore," Kosta said.
Registering is $185 for US residents or $210 for those outside the U.S.
The Chicago Marathon is in its 37th year. The race will be held in Chicago's Grant Park on Sunday, October 12.
"We think this is a fair way for our participant base to access entry into the race," Care Pinkowski, race director, said.
Those who fail to get into the Chicago Marathon can run one month later at the second annual Naperville Marathon, where there's no lottery.
"This race allows people to run an alternative to Chicago," Bob Hackett, Naperville race organizer, said.
Naperville organizers said they're fine with playing second fiddle on Novmeber 9.
"Everybody's gotta do Chicago, at least once," Pat Leonard said.
Naperville Marathon organizers said they have about 3,000 spots left open. They expect those to fill up once the Chicago Marathon lottery winners are chosen.