Several families visiting the city on Monday also made an unplanned visit a Chicago tow lot, and they say there was no signage prohibiting parking when they walked away from their vehicles.
The motorists included those visiting the Shedd Aquarium and Adler Planetarium.
Members of the Gleckler family said they parked around noon along East Solidarity Drive to visit the aquarium. They paid the meter through 6 p.m. but realized there was a big problem as their time ran out.
City crews already had the vehicle hooked up and on the move as Amy Gleckler and her family approached.
"We see our van going as we're coming," she explained. "If this was a 'no parking zone,' -- one, there was no sign up where we parked, and two, why are the meters working if we're not allowed to park here?"
A "No Parking / Tow Zone" sign on a parking meter spotted later in the day wasn't there hours earlier, the motorists said. The sign said parking was prohibited in the area from 1 p.m. to 11:30 p.m. for the Justin Timberlake and Jay-Z concert at Soldier Field.
Keith Wilson said he noticed no signs as of 4 p.m. He said he parked and paid the meter through 8 p.m. and didn't learn until later that parking wasn't allowed.
"I think that's wrong," he said.
A city spokeswoman said the signage had been posted since last Thursday.
"As it does at least 24 hours in advance of any concert or event, the Chicago Department of Streets and Sanitation posted signs clearly indicating the restricted parking conditions on streets near Soldier Field," spokeswoman Ann Sheahan said via email. "If an individual believes their car was towed in error, they can contest the tow through the city's adjudication process."