The kits, which date between 1986 and 2011, were never submitted for analysis, according to Cook County Sheriff Tom Dart.
The sheriff's office says all of the kits will now be submitted for testing, and the alleged victims will be contacted.
"You read some of the inital facts of some of these cases, they're pretty horrible. People being dragged into cars, people who have actually pointed out some of the individuals they believe did it," said Dart.
When a victim recants, it is not uncommon for police not to submit a rape kit. But Illinois law requires all rape kits gathered after 2010 to be tested regardless of circumstance.
"The public should have every reason to feel that when an event like that occurs that law enforcement is going to treat it as a priority. It's going to be on it immediately. And if you don't have the tools to do it, call in other people for assistance," said Dart.
The discovery comes just weeks after former Robbins Police Chief Johnny Holmes left the force after being charged with his second DUI in less than three years.
Residents at a community meeting on Tuesday evening said they were shocked.
"I just don't have any words for that. That's unconscionable," said Carlos Rhodes, Robbins native.
"I think it's going to be really, really hard for those individuals to understand that when they've done everything the criminal justice system has asked them to do," said Debbie Perry, YWCA Metro Chicago.