When Lollapalooza first made it's Grant Park debut in 2005, there were only a few dozen acts on five stages, and the two-day event attracted 65,000 people.
This year, for the 10th anniversary, organizers are expecting 100,000 people each of the three days, with 137 acts on eight stages.
The annual event has become securely entrenched in the city's culture.
"It's as synonymous with Chicago as blues music is, and house music, and it's resonating globally, which is helping us to achieve the mayor's goals for increasing visitation to Chicago," said Meghan Risch of Choose Chicago.
Weather is always something event organizers can't control. Rain can turn the grounds into a muddy mess and the entire festival had to be evacuated in 2012.
But the company that produces Lollapalooza, C3 Presents, foots the bill for any damages caused during the three-day event.
Last year, Chicago Police credited the beefed-up fencing and increased security with decreased crime at the festival and fewer fence jumpers.
"You're in the city of Chicago when you're at Lollapalooza and the city enforces the laws, so abide by the laws," Lollapalooza spokesperson Lindsay Hoffman said.