The flames came dangerously close to homes and apartments in densely populated, upscale neighborhoods like Lakeview and North Center.
According to the Chicago Fire Department, an arsonist ignited 12 fires in the four-hour period between 11 p.m. Tuesday and approximately 3 a.m. Wednesday -- while most people were sleeping. All of the fires were started in dumpsters.
"I think there's somebody out there who has a problem and needs to be stopped," said North Center resident Mike Schaeffer.
One of the fires in the 4000-block of Hermitage melted garbage cans in the alley. The flames spread to a nearby garage, which belongs to Rich Hoagland's sister.
"She just said one of her neighbors came knocking on her door at 2:30 in the morning and said, 'The alley is on fire. You need to go out there and see what's going on.' And she said she came out here last night, and the fire department had everything under control," Hoagland said.
The worst damage happened in the 3500-block of North Halsted Street, where a storage shack filled with alcohol for a nearby restaurant was torched.
Flames destroyed the structure, but no one was hurt, and no injuries were reported in the other fires.
"Those could spread really easily, and if it's in the middle of the night, people might not catch it," said Lakeview resident Alexis Peterson.
"It's kind of one of those things that we as residents have to be vigilant around here and watch what's going on, and when there's a problem happening or something doesn't look right, call 911," said Greg Rohner, also a Lakeview resident.
The Chicago Bomb and Arson squad is leading the investigation and trying to figure out if all of the fires are linked and who might be responsible. They say they believe the same person could be responsible for them all.
Authorities say they do not have a good description of the suspect. They do say, however, they might be looking for a man on a bicycle, a tip they say they got from witnesses.