Great Saltpetre Cave in Rockcastle County, Kentucky, became one of the state’s most important early sources of saltpeter, the potassium nitrate used in gunpowder. Discovered in the late eighteenth century by Robert Baker, the limestone cave’s dry soil and passable stream made extraction practical, and its operations helped inform Dr. Samuel Brown’s 1806 scientific account of Kentucky’s saltpeter industry. The cave was especially significant during the War of 1812, when sixty to seventy men, many enslaved, worked there and the mined material was sent to Lexington for gunpowder. Later reused during the Mexican–American War and Civil War, it eventually shifted from industry to tourism before preservation efforts took hold.