All that work was done by brave workers more than 1,400 feet above Chicago.
It's Part 2 of the project to help deliver a stronger television signal and better reception into your home.
Installing the new 35-foot antenna was quite a feat.
First the helicopter lifted up a piece called the "wedding cake" because of its shape which will help with the connection.
Then the antenna was lifted from the ground to the roof of the Willis Tower.
Waiting up there, workers readied to get the piece in place and bolt it down. Windy conditions made the procedure even more precarious.
"By the time they brought the first piece up it got rough," said John Rukavina.
The weather is a factor the workers have to think about, and also why it took months to gear up for this type of project.
"It's not so much picking it up down here," said Installation Services' Ronald Romano. "It's the top guys, when they get it up, line it up, they get it done that's what makes the job."
The two pieces of equipment weighed around 4,000 pounds each and required a lot of precision to get in place.
This project started in July, when the same team removed the old antenna from the top of the Willis Tower and got it safely to the ground.
That disrupted TV signals and traffic in the Loop.
The replacement is a high-powered antenna bringing you a stronger signal.
"You're going to see a new and improved signal so of our viewers a little further out from the Willis Tower will be able to receive us in a much stronger signal," said WLS-TV President John Idler.
After some tweaks, the new enhanced antenna will be powered up and transmitting.
During the transition, however, viewers can still watch ABC7 without interruption.