An estimated 40,000 runners will hit the city's streets Sunday for the 39th Chicago Marathon, which is expected to cause significant traffic delays.
"It's a lot more crowded, a lot harder to get anywhere," said Kimberly Richards, a marathon runner.
Near Grant Park, some street and lane closures closed on Saturday, including Columbus Road and Roosevelt Road.
"We've been trying to Uber a lot wherever we can, but it's just been a little difficult with the traffic," said runner Karen Nyholm.
Eventually a total of 39 streets throughout the city will shut down along with some expressway exit ramps as over a million spectators cheer on thousands of runners just after 7 a.m. Sunday.
"We've got 40,000 runners coming from all 50 states, 130 countries, and elite athletes all here in good form," said Carey Pinkowski, Chicago Marathon organizer.
The Chicago Marathon is not the only event causing a traffic gridlock. The start of the Cubs postseason at Wrigley Field, a Kanye West concert at the United Center, and President Barack Obama returning home for a democratic fundraiser and to play golf in the south suburbs are all factors adding congestion to the area.
"It took me a while to get back from the concert last night, not even just the concert, traffic for the marathon has been crazy as well," said Jamal Ransom, a concert goer.
City officials said using public transportation will make getting around easier, and although dozens of bus routes will be detoured, the CTA said it would add more subway trains and run them more frequently.