While 53-gallon (201-liter) barrels are the default for aging whiskey in the United States, it was not always this way, and many craft distillers are exploring barrel size as another tool to shape their whiskeys.
Although all whiskey must be aged in an oak vessel, the size of that vessel can vary widely—and historically it has, as the barrels originally used to store spirits were often reused storage containers made by hand, with no mind to any kind of standard size.
That tradition remains visible in Scotland, where barrels can range from refurbished quarter casks as small as 13 gallons (49 liters) to the gigantic port pipes that can hold upward of 172 gallons (651 liters). Until this past century, American whiskey barrels mirrored that level of variety. But for practical and economic reasons, domestic distillers eventually settled on new charred barrels of a standard size.