Corn whiskey is one of the oldest whiskey styles in the United States. It is legally defined as a spirit with a fermented mash of at least 80% corn. Corn whiskey can be bottled without oak maturation, and if aged, the process has to take place in used or uncharred oak barrels—unlike bourbon that has to be matured in new charred oak.
Corn whiskey appeared sometime in the mid-1700s, first among Scottish and Irish settlers who were familiar with the whiskey-making technique. It was a rustic spirit that was not aged and mostly intended for immediate consumption. Following the Civil War and federal and state taxation, most of the production went underground, and corn whiskey became American moonshine.
It is especially favored as a cocktail ingredient that provides depth and character. Although it is somewhat difficult to pinpoint the exact flavors in corn whiskey, it usually has a rich corn flavor with a long, somewhat sweet finish. Unaged styles are fresher, while matured varieties tend to develop delicate spicy notes.