Historical Marker #715 in Rockcastle County commemorates the importance of the "Great Saltpeter Cave," a large cave located south of Mt. Vernon. There, organic materials were mined to create gunpowder during the War of 1812.
Sulfur, charcoal, and saltpeter create gunpowder, and during the nineteenth century Kentucky's extensive cave systems, including Mammoth Cave, were important sources for saltpeter. During the War of 1812, Kentucky's caves played an important part in the American war effort.
In many instances, including at Mammoth Cave, wooden frames were built within the caves and were filled with dirt from the cave floor. Water was filtered through the dirt, which contained calcium nitrates, or saltpeter. The water containing the saltpeter was then filtered and boiled, leaving saltpeter crystals that were transported to factories to make gunpowder.
Therefore, several of Kentucky's most important War of 1812 sites were caves, including Mammoth Cave and the Great Saltpeter Cave in Rockcastle County.