Meramec Caverns is a set of natural limestone caves that features beautifully sculpted patterns of stalactites and stalagmites. Formed more than 400 million years ago, the caverns have a long and rich history. First used by Indian Tribes as a shelter, they were first discovered by "white men” when a French Miner stumbled upon them in 1720. Discovering saltpeter in the cave, which is used to make gunpowder, Renault named the cave Saltpeter Mine and mined the resource until 1742. Later, Spanish miners utilized the cavern as a base of operations for lead mining. During the Civil War, saltpeter mining was revived in the cavern and Union troops used it as a munitions powder mill from 1862 to 1864. However, when William Quantrill and his irregular band of Confederates discovered it, they destroyed the plant. One member of Quantrill’s band, namely Jesse James, would remember the location of the cave and use it later during his outlaw years. It was also during this time that the cave was said to have harbored runaway slaves on the "Underground Railroad.” On the way to Meramec Caverns, another vintage business -- the old Riverside Reptile Ranch, can also be seen.