Saltpeter, Gunpowder, and the War the Cave Armed

Before anyone thought of the cave as a tourist destination, before Stephen Bishop mapped its deepest rooms, the cave was a mine. What miners were after was not ore. It was the cave's dirt.

The soil and breakdown rock of Mammoth Cave is saturated with calcium and magnesium nitrate, the raw material for potassium nitrate, which was also called saltpeter, which was the indispensable ingredient in gunpowder. The cave had been accumulating nitrate-rich guano from bats and organic debris for tens of thousands of years. In the early eighteen hundreds, that accumulation was worth more per pound than most anything else a Kentucky farmer could produce.

Beginning in eighteen twelve, after Charles Wilkins and Hyman Gratz purchased the cave, a large-scale extraction operation ran inside through the War of eighteen twelve, using enslaved labor to dig the nitrate-bearing soil into large wooden vats, leach it with water carried in wooden pipes, and process the resulting liquid into usable saltpeter. The War of eighteen twelve was being fought largely at sea and along the Canadian border, but the gunpowder for American ammunition was being made from material extracted from this darkness, by men whose names are not in the documented record.

The wooden infrastructure from the saltpeter mining period is still inside the cave. The leaching vats, the wooden pipes, the conveyance structures: all of them have survived in the cave's dry, temperature-stable atmosphere for more than two hundred years. They are among the best-preserved examples of early American industrial technology anywhere in the country, maintained not by preservation effort but by the simple fact that the cave holds time differently from the surface world.

The cave became a tourist attraction because the saltpeter operation stopped. The mining company abandoned it when the war ended and the market for saltpeter collapsed. What they left behind became the first exhibit in a history the cave has been accumulating ever since.