There have been bison at Fermilab for some years, but they are just over the border in Dupage County, not Kane County.
Kane Country has had cougars for quite a while. :)
There's a couple dozen at Midewin, too: https://www.fs.usda.gov/r09/midewin/animals-plants/bison-pro...
I honestly thought Fermilab was in Kane. I could see it from my front yard growing up west of Geneva.
The Fermilab herd was always one of the highlights of visiting there. I always thought that was a really good use for the space inside the accelerator, a nice version of nature and science coexisting. I have it in my head that we used to be able to just drive through Fermi to see the Bison (late 80s/90s).
More on the bison at Fermi: https://www.fnal.gov/pub/about/bisoncam/