Kentucky Spirits: What Makes Bourbon Bourbon?

View of the end of a cask stamped with the distillery name and batch.
A bourbon barrel at the Woodford Reserve Distillery in Versaille. Photo © wanderstruck, licensed Creative Commons Attribution.

Remember in geometry class when you learned that all squares are rectangles, but not all rectangles are squares? Well, bourbon is just like that. All bourbons are whiskeys, but not all whiskeys are bourbons. For a whiskey to be a bourbon whiskey, it must meet a very specific set of criteria.

  • It must be made with at least 51 percent corn.
  • It must consist of only grain, yeast, and water. No color or flavor can be added.
  • It must be aged in brand-new charred white oak barrels for a minimum of two years.
  • It must be distilled to no more than 160 proof and barreled at no more than 125 proof.
  • It must be bottled at no less than 80 proof.

Additionally, as America’s only native spirit, bourbon must be distilled in the United States. Although technically, it can be distilled anywhere in the country, 95 percent of the world’s bourbon comes from Kentucky. Two things in particular make Kentucky an ideal place to produce bourbon. The first is the abundance of limestone springs, which produce water that is rich in nutrients but free of flavor. The second is that Kentucky has four very distinct seasons. When bourbon enters the barrel, it is a clear liquid not all that different from moonshine. When it exits the barrel, it is an amber-colored liquid rich with flavors that range from vanilla to spice to caramel to butterscotch.

All of bourbon’s color and flavor comes from the charred white oak barrel. The charring brings out the sugars in the wood, which the bourbon then absorbs through a process of expanding into the barrel during hot Kentucky summers and then contracting out of it in cold winters. Different varieties of bourbon are produced through both alterations in the recipe and changes in the amount of time the bourbon ages.

Now about the name bourbon. Many residents of and visitors to Kentucky think that Bourbon County was named for the drink, whereas, in fact, the drink was named for the county (which was named for the French royal family). Once an enormous county, Bourbon County was home to the Ohio River port, from which barrels of Kentucky corn whiskey were shipped out to the rest of the country. As the barrels were loaded onto boats, they were stamped with the word “Bourbon” to indicate their port of origin. As Kentucky whiskey gained a following, people began to refer to the liquor as bourbon thanks to the stamp on the barrel. The name stuck, and the best whiskey in the world has been known as bourbon ever since.

Excerpted from the Second Edition of Moon Kentucky.