On Illinois 1 just south of I-74 and Danville is Mike's Grill, a 50-year-old drive-in. I stopped there recently and tried the breaded pork tenderloin sandwich and a cheeseburger.
It was OK. Not great but not terrible, and its main flaw was that it was too greasy for me. Fortunately I ordered it with mustard so the vinegar helped out a little bit; with mayo or other non-acidic condiments it would've been a lot worse. The shape is random enough to make me think it could be made by hand from scratch but it was also ready very quickly...maybe the BPTs are made in advance and kept in the fridge until needed?
Right next door is Mike's Chill, an ice cream stand. I'll bet it's a popular place on warm summer evenings but it was pretty dead at noon on a Wednesday.
And my sandwich, eaten at a nice public park a few miles south in Westville: