The Bank of America Chicago Marathon is in in its 36th year, and 45,000 runners are registered for the October 13 event, which starts in Grant Park. Millions of people gather each year to line the 26-mile route and cheer them on.
This year, security will be on the minds of runners and spectators at this weekend's marathon.
The Chicago Marathon on Sunday is the first of the world's major marathons to be held since the Boston Marathon last April.
Marathon organizers are saying the security shouldn't change the experience for the runners nor for spectators.
There will be an unprecedented amount of security as a result of what happened in Boston.
Fences have been installed along Columbus, which is the site of the marathon's start and finish line.
There will be four check points for runners to enter Grant Park and other security changes, but police and race organizers say it will not detract from the experience.
Todd Sipe is getting set to run his 30th marathon, his eighth in Chicago. Todd and all 45,000 marathoners, will for the first time, be given a clear plastic bag to carry their belongings. That's meant to enhance and expedite security.
"I'll feel more secure. I think all the stuff I need to bring to it will fit in the bag so there's no problem for me at all," said Sipe.
Also, unlike years past, runners must personally pick up their own race packets beforehand. No longer can they pick up bibs for others.
A 26.2-mile route with thousands running and thousands more watching is a huge challenge, but Chicago police have a template they'll build on. The Blackhawks Stanley Cup parade, which came two months after the Boston bombing. Although the Hawks rally was clearly a different type of event, it incorporated lessons learned from Boston.
Much of the route is lined with cameras which will be monitored live. Getting into the reunion area, off the finish, where friends and family come to congratulate the exhausted will include bag checks.
"What happened in Boston has not deterred the marathon spirit," said Carey Pinkowski.
"In some sense, they're more determined to run and be at larger events to show that what happened in Boston isn't going to affect who they are, or change what they do as a runner," said Wendy Jaehn of the Chicago Area Runners Association.
More details on the race are available at chicagomarathon.com.