It seems that the inspiration for Mater (the tow truck) came from a place along old 66 in SE Kansas, just across the state line from you, GLC. I think it's in Baxter Springs, right?
A little story about how we came to see Cahokia Mounds: Back in 1993, my husband and I had a road trip planned to Washington DC. His parents wanted to keep the kids, who were too young to really get much appreciation for the springs, and we were coming up on a wedding anniversary. So one morning, we left mid-Missouri early in our 1987 Ford Aerostar, heading east.
We discovered I-270 on that trip, but it was also the year of the Big Flood on the MS and MO Rivers. We had just crossed the state line/river into Illinois and were admittedly looking around at all the water -- and a van had been going waaaaay too slow for the freeway. I remember screaming "LOOK OUT!" and we went right into the back of that van as my husband braked HARD. Next thing I knew (I blacked out), we were in the median strip with the other van and there was a policeman taking down the information, getting us into an ambulance. Long story short, we were okay except a bit dazed, the van we hit had a passenger who broke his arm (not wearing his seat belt and he went into the dash, he was lucky and so were we). Our insurance company took good care of us, got us a rental car, and instead of going on to DC, we canceled our DC plans, spent a couple of days poking around the Granite City IL area, and then went back to pick up our girls as we only had a week to get back home. That's when we went to Cahokia Mounds, and a STL Cardinals baseball game.