Whiskey has always been a popular and important American spirit. However, it wasn't until the Prohibition era that whiskey production was diversified and different styles of whiskey came to identify with specific regions of the United States. The conditions of prohibition may have given rise to the popularity of whiskey, but the end of prohibition brought it into the mainstream.

When the production of alcohol was banned by the 18th amendment, alcohol producers were required to take production and distribution underground. Because of the risks involved with transporting and storing alcohol during prohibition, high alcohol by volume spirits increased in popularity. High alcohol by volume liquors such as whiskey, rum, and gin pack more potency in smaller, easily concealed containers. The popularity of high proof liquors lead directly to the creation of cocktails and mixed drinks. The alcohol had to be cut with other mixers in order to stretch out smaller supplies of liquor. In this environment, innovative speakeasies developed many popular whiskey-based cocktails such as the whiskey Old Fashioned and the Manhattan.

The effect on production was even more pronounced. Many distillers moved their operations deep into rural areas where they could hide stills in barns, forests, caves, and basements. For many of these outlaw distillers, whiskey was their product of choice due to the abundance of corn and other grains. Whiskey is distilled from fermented grains, especially corn. In fact, bourbon, the most common American whiskey, must be made from a grain mixture that is at least 51% corn. These grains were widely available and could be purchased in bulk under the guise of animal feed by farmers without arousing suspicion from local authorities. Once the whiskey was distilled, moonshiners would store it in oak barrels, often underground. Many of the flavors and aromas commonly known to whiskey drinkers come from storage in oak barrels. Although the use of oak barrels was once a necessity to hide whiskey from the feds, many of today’s high end whiskeys get their signature flavor notes from storage methods that have their origins in the Prohibition era.

When the 21st Amendment was ratified on December 5, 1933 and legal liquor began to flow in the United States again, former outlaws went legitimate. This lead to the regulation of alcohol and stricter definitions of different spirits. Since industry sought to define different types of liquor, the distillers had to discuss what makes whiskey different from rum or gin. Apart from the obvious difference in fermentation products, whiskey distillers essentially engaged in an exchange of the best practices they had developed during the outlaw days of prohibition. Of course, the minimum standards of whiskey leave a lot of room for individual distillers to continue to produce nuanced, full-flavored whiskeys with unique appeal.

Whiskey connoisseurs might look at the Prohibition era as a dark time in American history. However, it led directly to today's era where whiskey distillers are true artisans and the making of whiskey has been elevated to an art.