Saltpeter or potassium nitrate was of key importance to the survival of early settlers in what is now West Virginia. Saltpeter was used by settlers to salt meat and to make dyes, and it was a key ingredient in gunpowder, which was made by mixing small amounts of sulfur and charcoal with saltpeter.

The earliest explorers in the region brought a supply of gunpowder with them. Soon, it was discovered that naturally occurring saltpeter could be found in the many limestone caves and sandstone shelters. Noncommercial mining of saltpeter began prior to the American Revolution, and the caverns of Western Virginia were a major source of saltpeter for the colonial army. Commercial production continued through the War of 1812 and then fell off after the war ended.

During the Civil War, the Confederates made extensive use of these mines to make up for the loss of other saltpeter sources due to the Union blockade. Twenty-two caves in present West Virginia were mined between 1862 and 1865. Confederate miners often produced the saltpeter entirely underground to avoid detection, but many mines were discovered and the workers imprisoned. Schoolhouse Cave in Pendleton County is the only cave known to have been mined for saltpeter by Unionists during the Civil War. Following the war, saltpeter mining was discontinued as new technologies rendered the mines obsolete.

Saltpeter was produced by simple but effective methods. Earth was shoveled into wooden hoppers and water poured in to leach out the saltpeter. The water was then evaporated, leaving the valuable saltpeter. Many artifacts of the process have been found in West Virginia caves, including hoppers and tools. Such artifacts may be seen by visitors to Organ Cave in Greenbrier County.