Much like sourdough bread, the name "sour mash" comes from a unique whiskey production process whereby some of the previously fermented grain mash is used as the starter for a new mash to be fermented. Neither a rye whiskey or a bourbon, this complex and flavorful style has quickly risen in popularity. Michter's "US-1" offers notes of burnt sugar, spice, smoky fruit, candied cherries, honey, and vanilla. Smooth like bourbon, spicy like rye.