We just stayed here overnight while traveling I-70.  We will always choose a state or national park over an RV park for overnighters if they are 1) open and 2) not too far off on main travel route. Trip included, of course, a stop in St. Louis at the Arch.

Campground: Graham Cave State Park
Location: Danville, Missouri
Cost: $19
Services: E
Comments: A pleasant enough state park off I-70 for easy on and easy off.
Link to Map in “Where We’ve Been”

St Louis Arch

The famous Arch