Be made in the United States, 95% of bourbon comes from Kentucky, but it technically can be made anywhere in the USA
Contain at least 51% corn in the fermented grain mash.
Distilled to no more than 80% alcohol by volume must be no more than 62.5% ABV (125 proof) when it enters the barrel
And most importantly, must be stored in BRAND NEW charred oak barrels. It is these barrels and the charring that give bourbon its unique characteristics, which means the barrel can be used only once for bourbon.