Being from Missouri and camping primarily in Missouri for over 60 years I could recommend several spots, depending on you likes and wants, RV requirements and comfort levels. All the previous posters are correct and there are a ton of things to see and do. DW & I are constantly finding new places and interesting thing to see & do.
A nice quiet park 60 minutes south of St Louis if Hawn SP. Nice trails and a nice quite park. Not far from Ste Genevieve, historic MO town. As mentioned before Roaring River SP is our favorite, but we trout fish. Beautiful area and not far from Eureka Springs, AR.
I could go on and on. PM me, if you wish, with your requirements, interests and questions.