This is a controversial topic that I'll make no apologies for. If you're curious about where the most heavily-armed county is in America, you don't need to travel far. It's right across the border from Illinois.
Illinois is the only state in the region that requires a Firearm Owner Identification (FOID) card to possess a firearm and/or buy ammunition (the constitutionality of that requirement being challenged at the State Supreme Court).
The Illinois State Police (ISP) are well aware of the incredible backlog of Illinois Firearm Owners Identification Cards (FOID) and concealed-carry licenses (CCL) waiting to be renewed, and because of that, they've given a 150-day extension to those of us who've seen our cards expire.