QuakeCon
Not that I expect someone who lives on the west coast to know, but that's not in the midwest. It's in the center, but I'm in the North (Minnesota) and that's in the South (Texas), so while it would be a shorter drive than Pax, it's still not an event which I could consider going to until I have a considerable cash flow.
I'm sure there are some smaller gaming events, probably in Chicago, but the majority of gaming events people talk about (e3, GDC, Pax) are all on the west coast. Sure most of the developers are out there, but that doesn't mean most gamers are.