European American settlers and entrepreneurs recognized the cave primarily as a source of calcium nitrate — saltpeter — which was a critical ingredient in gunpowder.

During the War of 1812, when a British naval blockade cut off the United States from Caribbean sources of saltpeter, Mammoth Cave was developed as a domestic source.

Enslaved workers — ultimately about 70 people, some enslaved and some indentured — were brought into the cave to mine saltpeter, following wooden pipe systems and vats to process the cave earth for its nitrogen content.

The saltpeter operation left its own physical traces in the cave, some of which are visible today: the wooden pipes, the processing vats, the pathways worn smooth by the labor of enslaved workers in the first decades of the nineteenth century.