I hunt the castor, & there are quite a few fossils there. but my favorite places for fossils are road cuts. That's where I have found some of the best. There is a book called Roadside Geology of MO. It's fairly new. I also Have one for Idaho &
WYO. Used them a lot when I was there. I have also used this link to ID some of my materials, plus it is a fun site to track. Main menu, I-170 Pennsylvanian exposure (Altamont Formation)