I chose to stick to the back roads today and didn't regret my decision; the hills gradually gave way to plains. I saw a return to soy and sorghum but on a field by field basis. Other fields were hay, pasture, clover, sunflowers, and even some winter wheat.
I was feeling some anxiety about Internet errands, so I stopped in Liberal, MO, just outside my destination of Prairie State Park. I found that PSP was my only camping option for the night. When I got to PSP, I found that the campground is the only part of the park not enclosed by fences and cattle guards: bison roam free. You're supposed to check in at the visitor center to find out where it's safe to be outside a car, but the visitor center is surrounded by area where you're not supposed to be outside a car... and the center was closed for the night anyway! So I just helped myself to a primitive campsite (no showers or electricity).