There was a wild cougar hit by a car and killed on route 173 about 2 years ago. It was up by the Chain of Lakes State park where apparently the cougar had been living life large on the big corn fed white tails we have up there. No doubt the deer had forgotten about cougars and were easy pickings. You could walk across IL. on the huge deer without ever touching the ground. It should come across as no surprise that cougars have made it back this way.
It wasnt killed in a suburb. It was killed in the city. Theres a river/canal that goes by just west of the area the Lion was killed in and it connects, thru forest preserves, directly to the Chain Of Lakes ecosystem, which connects to other watersheds far to the west. We used to see bobcats, deer, coyotes, all the time working midnights in the area the Lion was killed. No doubt the cat just followed this watershed feeding on the abundant deer, rabbits, coyotes, and birds. The North Branch watershed goes all the way thru the city and connects to the north to the Skokie Lagoons, the botanic gardens, all the way to the Chain of Lakes.
Which btw is part of the Mississippi watershed. So you see its very easy for Mountain Lions to have made their way back east. And now its spring time when all our zillions of waterfowl and deer are dropping babies. Like would be good for the enterprising lion who aint afraid of a big adventure.