A distinctly American whiskey, bourbon is considered America’s "native spirit" with its historical, cultural, economic, and social influence. But, what is bourbon anyway?

There are five rules to classify a whiskey as bourbon: it must be made in the United States; the mash must be at least 51% corn; the whiskey has to be aged in a charred, new-oak barrel; the proof can’t be higher than 125 when entering the barrel; and it can’t surpass 160 proof when distilled. In honor of  #NationalBourbonHeritageMonth, here are a few more facts about bourbon.

Kentucky doesn’t have sole claim on bourbon.

Although Kentucky produces the largest amount of bourbon, to the point where there are almost two barrels for every person living in Kentucky, it’s not the only state to venture into making bourbon. Plenty of other states, including New York, Virginia, and Indiana, produce craft bourbon spirits that are equally as delicious as Kentucky bourbons.

There’s no minimum age requirement.

While you still have to be of age to enjoy a neat glass of bourbon, there is no specified minimum age for whiskey to be considered bourbon. There is a loophole, since distillers are required to label if the bourbon had been aged for less than four years, and Straight Bourbon has to be aged for at least two years.

The Angels take their share.

About three to four percent of bourbon naturally evaporates during each year of barrel aging. This can total to about a third of the total product after 10 years. This natural occurrence is called Angels’ Share, as it’s thought to have escaped to heaven to satiate the angels.

Distilleries produced penicillin during WWII.

Many Kentucky distilleries were altered to produce penicillin during World War II, since like bourbon, penicillin is produced through fermentation. While it was in short supply, distillers came in clutch to help produce the antibiotic.

Barrels can only be used once for bourbon.

The charring of new-oak barrels give bourbon its beautifully infused notes of toasted caramel and vanilla. Once the barrel has been used, it can’t be reused for bourbon and is passed on to scotch producers to age their scotch in.