Salt has been used as a preservative for much of human history. The first recorded use of salt in meat preservation actually began with the ancient Sumerians around 3000 BC. The Sumerians were the first recorded people who salted and dried meat for curing purposes. Salt with nitrite was also used to preserve meat by the ancient Greeks; however, their use of it was not deliberate as they were unaware of the presence of nitrite since it was an impurity in the salt. The ancient Romans would learn of curing meat from the Greeks and would note the reddening effect of the nitrite but no one would understand its role until much later in history.
Curing salt is also known as Prague Powder or pink salt; however, it is not to be confused with pink Himalayan salt and should not be used in the same way. If you were to look up recipes containing it, you would find that many specifically refer to it by the Prague powder name rather than as curing salt. While there are many who speculate that Prague powder came from the city of Prague in the Czech Republic, its roots (and the roots of the name) are much less exotic. Curing salt was actually invented at the start of the 20th century as scientists identified the nitrites that could be used to preserve meats. Salt was also used during the Middle Ages in Europe, where salt beef became a popular food.