In 1964, congress made bourbon the national spirit.
To be official it must made with at least 51% corn. It must be aged in charred new oak barrels. It must be stored at no more than 151 proof and bottled at no less than 80 proof.
It doesn’t have to be distilled in Kentucky, but it must be made in the USA.
After the barrels are used once, they are shipped to Scotland where they are used to age scotch.