real simple googling points out what I've read in several preservation books. Per wikipedia: "In the process of food preservation, potassium nitrate has been a

real simple googling points out what I've read in several preservation books. Per wikipedia: "In the process of food preservation, potassium nitrate has been a common ingredient of salted meat since the Middle Ages" SaltPeter has been around for a long time. Given that nitrates/nitrites help with botulism and the age of discovery & uses, I'd be surprised if it was a modern (post 1800's) thing, and wiki backs me up. For sure by the time Europeans were heavily in north america it would be in wide spread use. I mean they were using it for gunpowder too :) When using them, you don't use much, but you use it. It also means you can use less regular salt.