IL, bow and shotgun, then there is also a muzzleloader and a handgun season as well. No modern rifle, at least in my neck of the woods.
Someone more educated could give you a reason why.
I always assumed it was legislation passed down because of Chicago.
But then again, I could be terribly wrong.
Ohh, and to answer you final question, in my county (Grundy), I can't bowhunt during shotgun season. So I am limited to hunting with my shotgun during the twofirearm seasons. Not all counties in IL are like that though, as I was corrected here just a few months ago.

Don't remember the correct answer though.
So basically, I have lost all my credibility through this post. HA.