"One of his first questions this morning was 'when can I get back on the treadmill?'" said Dr. Edward Hollinger, Johnson's transplant surgeon.
Johnson received a kidney from his 25-year-old son Daniel. A hospital spokesperson said surgeries on both Johnson and his son went smoothly and as expected.
Daniel was released on Thursday. The superintendent is expected to be released over the weekend.
"Love and support has been overwhelming...my family really appreciates it and I really appreciate it," said Johnson's son.
Chicago Mayor Rahm Emanuel visited Johnson in the hospital and said the superintendent was in good spirits, sitting up.
"Looks great, sounds great, his spirits are up," said Chicago Mayor Rahm Emanuel.
The operations were performed by Dr. Martin Hertl and Dr. Edward Hollinger and their surgical teams, the hospital said.
The 57-year-old superintendent said he's been waiting 31 years to feel better. He also emphasized the attention on his surgery isn't just attention on himself, but the importance of organ donation overall.
Johnson's private medical issues became public back in January, when he fainted during a press conference and it was caught on camera. The superintendent said that experience has encouraged others to visit doctors and seek treatment if they think they have the same issue.
When it was clear Johnson's kidneys were failing, his son, Daniel, stepped forward and offered to be a living donor. If his son hadn't offered his kidney, it would've been a long wait. The national waiting list is 100,000 deep. On average, it takes five years before there's a match.
Johnson arrived at Rush University Medical Center around 6:10 a.m. Wednesday and spoke to the press. He said he's feeling great, but is anxious to a complete the procedure.
"I just really want to thank the citizens of Chicago. The support my son and I have gotten is unexpected and overwhelming. I really don't think that Webster's Dictionary has the word in there yet, that really can describe that feeling. So, thank you," Johnson said.
He said he's proud of his son for stepping up, for choosing to donate and for helping raise more awareness about how many lives can be saved through organ donation.
"I'll tell you this. The whole journey, to this point, is not about Eddie Johnson. It's about shining a spotlight on organ donation, period. But I'm proud of him because it's a decision that he made on his own. It's humbling, because it's not an easy thing, I'm sure, to make that decision. But it just highlights how important it is for people to do organ donation," Johnson said.
Johnson was put on an intense exercise routine since the transplant was scheduled, to prepare his body for surgery and recovery. He said he's been doing about 40 minutes of cardio a day and has been eating healthier. He said he's lost about 50 pounds since Feb. 1, and it feels good.
"The difference between how I feel physically today as compared to this time last year is like night and day," Johnson said.
He'll spend three to five days in the hospital after surgery and three to six weeks at home to recover.
WATCH: Doctor explains kidney transplant surgery