For a whiskey to qualify as bourbon, the law -- by international agreement -- stipulates that it must be made in the USA. It must be made from at least 51% and no more than 79% corn, and aged for at least two years. (Most bourbon is aged for four years or more.) The barrels for aging can be made of any kind of new oak, charred on the inside. Nowadays all distillers use American White Oak, because it is porous enough to help the bourbon age well, but not so porous that it will allow barrels to leak. It must be distilled at no more than 160 proof (80% alcohol by volume). Nothing can be added at bottling to enhance flavor or sweetness or alter color. The other grains used to make bourbon, though not stipulated by law, are malted barley and either rye or wheat.
Bourbon is amber colored, and a little sweeter and heavier in texture than other whiskeys. Bourbon gets it’s name from Bourbon County in Kentucky where it originated.