Jack Daniel's Tennessee Whiskey is the single best-selling American whiskey in the world. Though it meets the requirements to be considered a bourbon, the distillers have eschewed that label since the brand's inception, instead opting to refer to it as a Tennessee sour mash whiskey. "Sour mash" refers to the technique of reusing some of the fermented solids from previous batches to ensure that fermentation stays more or less consistent.
Jack Daniel's was founded sometime in the late 1800s (probably 1875) by Jasper Newton "Jack" Daniel in Lynchburg, Tennessee. The whiskey's first brush with fame came with a gold medal at the 1904 St. Louis World's Fair, and despite the temporary setbacks of Prohibition, it went on to become the most famous Tennessee whiskey in the world. Ironically enough, Jack Daniel's home county of Moore is a dry county, prohibiting any alcohol sales within its borders.