Saltpeter Production in Shirakawa-go
Traditionally, one of the main industries in Shirakawa-go was the production of saltpeter (potassium nitrate) from the mineral niter, an essential ingredient in gunpowder. The required techniques were introduced from nearby Gokayama, where the industry had grown exponentially after the introduction of European matchlock guns in 1543. Villagers made saltpeter in a hole up to 2 meters deep near the irori fireplaces of their houses. They sold the crude product to one of the three licensed refineries in Shirakawa-go, where it was refined into saltpeter crystals. The refineries sold the saltpeter to domains and traders as far away as Osaka. Their largest client was the powerful Kaga domain (today’s Toyama and Ishikawa Prefectures) on the Sea of Japan coast, which at its height purchased more than half of all the saltpeter produced in Shirakawa-go. One merchant authorized to deal exclusively with the lords of Kaga had by 1788 accumulated a fortune sizable enough to build what was then the largest and most lavish house in all of Shirakawa-go. The saltpeter industry flourished until the Meiji era (1868–1912), when a cheap alternative was imported from Chile, resulting in a decline in local production.