A whiskey can only be called a Bourbon if it meets several requirements. 1. It must be made in the United States. (it is not required to be made in Kentucky as commonly supposed as there are bourbon distilleries in Virginia, Tennessee, and small bourbon distilleries elsewhere too). However bourbon, like the name Whiskey (spelled with an "e") is limited to the United States. 2. The raw alcohol must not have additives and must be stored in only a charred oak barrel for a minimum of two years. 3. The grain content can vary but must have at least 51 percent corn. 4. It cannot go into the barrel above 125 proof, and the best whiskey is diluted to between 40 and 45% alcohol.