American whiskey is a distilled spirit produced in the United States from fermented grains. It originated in the 18th century when British and Irish settlers introduced whiskey production. There are several styles of American whiskey defined by their grain content and production process, including bourbon, corn, rye, Tennessee, and wheat whiskey. Bourbon whiskey must contain at least 51% corn and be aged in new charred oak barrels, while Tennessee whiskey is filtered through charcoal before aging.