During the 1970s and 1980s, Michter’s Original Sour Mash was the distillery’s single most popular product. While the “Sour Mash” moniker originated from the whiskey production process of the same name – whereby some previously fermented mash is used as the starter for the new mash to be fermented, much like making sourdough bread – Michter’s Sour Mash earned distinction for its taste, combined with its unique grain selection. In fact, it can't really be categorised as a rye or a bourbon.