This is one place https://knifeade.com/illinois-knife-law/
I agree that blade length isn't payed much attention other than in the NE part of the state and a few other locals. As long as you aren't using a longer blade for criminal useage.
Just keep thinking about what I had to go through. You're on easy street. I'd make fun of you but having been there , I will give you a wee bit of slack.