Navy Pier filled to capacity more than two hours before the scheduled start of fireworks there, officials said.
Anyone who's already on the pier can stay to view the fireworks, but if they leave, they won't be let back on, according to a release from the Pier just before 7 p.m.
Mayor Rahm Emanuel ended city-run lakefront displays after taking office in 2011, and the official fireworks now take place at Navy Pier. Navy Pier's on-site parking garages were full before 2:30 p.m., according to a spokeswoman for the pier. Three off-site parking garages are offering discounted parking for the day.
And with July 4 falling on a Friday with sunny skies and mild temperatures predicted, officials had prepared for huge crowds they had expected to fill the pier to capacity long before the 15-minute exhibition starts at 9:30 p.m., according to Navy Pier spokesman Nick Shields.
As capacity for Navy Pier was reached around 7 pm, visitors who had been turned away sat in the grass in front of the pier, walked to nearby beaches or stood around wondering where to go.
Kristin Hemerley, 27, was trying to visit her husband who works on the pier when she was turned away at a metal gate set up under a sign for the Chicago Children's Museum around 7:30.
"I was gonna surprise him," she said. "We haven't spent a holiday together in a long time."
She brought her son with her in a stroller for his first Fourth of July and traveled almost two hours by public transportation to reach the pier.
"I traveled a long way," she said.
Rafael Leon and Pedro Sanchez were calling their friends who were already at the end of the pier, lamenting their decision to drive out from Pilsen.
They wished there would have been a sign to tell them it was closed before they spent 30 minutes looking for parking, they said.
"We never come here for this reason," Sanchez said. "I don't think we'll ever come back here."
Emily O'Callahan and Rachel Lopez of Logan Square stood in front of the gate with strollers, wondering what to do after they were turned away.
"It's just annoying that we made the trip down here just to get turned away," O'Callahan said.
They looked around the crowd and said they thought they might try to sneak in.
Officials expected about 125,000 people to pass through the pier throughout the day, compared with about 60,000 on a typical warm summer Saturday, according to Shields. He declined to give the capacity for the pier.
Overflow parking will be available for $15 at the Grand Plaza Self Park on North State Street, the Ogden Plaza garage on North Water Street and the Millennium Park Garage, Shields said. Drivers will need to get parking tickets validated at a designated location at Navy Pier to qualify for the reduced rate, he said.
For those who don't want to brave the crowds, Navy Pier will have regularly scheduled fireworks at 10:15 p.m. Saturday.
The former city-run July 3 fireworks at the lakefront, for most its run in Grant Park, begun for Bicentennial celebrations in 1976 under Richard J. Daley and routinely drew crowds of about 1 million as part of Taste of Chicago.
Emanuel's predecessor, Richard M. Daley, switched in 2010 to three simultaneous displays, on the North Side around Montrose Beach, on the South Side near 63rd Street Beach and downtown at Navy Pier.
Emanuel ended the city-sponsored lakefront displays in what he said was a cost-cutting move.