While the River King Mine Train is not the most thrilling ride in the park, it is one of the first roller coasters that many kids will get to ride, and because of that, it is a Six Flags St. Louis treasure to me.
Once upon a time, the River King Mine Train actually had a second train that ran in the building nearby that currently holds haunted houses during the fall.
The one side that remained is another great mine train that was developed by Arrow Dynamics, a company that I have yet to find a bad coaster from. A few banked turns and a couple of lift hills all set up the final drop into a black tunnel that ends the ride just right as a "mine train".
PS - Keep an eye out for a groundhog at the beginning of the ride near the station. Group of us saw him/her multiple times this summer.