Bourbon must be distilled from a mash at least 51% of corn. Malted barley, wheat, rye may be used for blending. Bourbon's sweetness and softness come from corn. Jim Beam is made from corn, malt and rye.
Early settlers began to produce whiskey in kentucky mainly because of the rich natural resrouces such as iron-free limestone water, oak trees to make barrels, grains and the ideal temperature to mature bourbon.
Jim Beam American Post: