During the 1970s and 1980s, Michter's Original Sour Mash Whiskey 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 Original Sour Mash earned distinction for its unique taste. With its unique grain selection, it cannot be categorized as a rye or a bourbon. After disappearing from the market in 1989, Michter's Original Sour Mash Whiskey made a triumphant return in 2012 with its introduction into the US1line. Staying true to the profile and palate of its predecessor, Michter's US1Sour Mash has quickly become a favorite of whiskey enthusiasts.