The 26-foot recreational craft that was carrying four people crashed sometime between midnight and 5 a.m., Illinois Conservation Police Sgt. Joshua Mooi said.
Crews recovered the boat but none of the missing boaters were initially located, Mooi said.
A body was recovered several hours later about three miles from where the boat was found.
The victim was identified as Elmer Jimenez, 32, of East Chicago Indiana, according to Illinois State Police.
State police said they believe Jimenez was on the boat when it crashed earlier in the day. No details about the crash have been given. A death investigation is ongoing.
The Coast Guard said there were four boaters on the vessel when it overturned. The body is believed to be one of those boaters; the other three remain missing. The Coast Guard said the last any family made contact with anyone on the boat was early Wednesday morning.
The search for the missing boaters has been suspended as of 6 p.m., the Coast Guard said. The Chicago Police Department Marine Unit, Chicago Fire Department, and Illinois Department of Natural Resources were also involved in the search.
The Sun-Times Media Wire contributed to this report.