About an hour out of St L is Graham Cave State Park. It's a nice park, as is all Missouri State Parks. Not much to write home about, but nice for a stop over. It's been a while since we've been there so I can't give a proper review. About 2 1/2 hours out is Arrow Rock State Historic Site/ State Park, which I highly recommend. Very unique as that it is in walking distance (1/2 mile) from the historic town of Arrow Rock. Well worth seeing for young and old alike. Start of the Santa Fe Trail, home of George Caleb Bingham, famous painter, historic J. Huston Tavern, which dates back to 1834 and provides a dining experience in the oldest continuously operating restaurant west of the Mississippi River.
But it is further than you wished. But still worth a visit.
