The Eighteenth Amendment to the Constitution of the United States prohibited the "manufacture, sale and transportation of intoxicating liquors." The amendment, passed by Congress in 1917, was written to become effective one year after its ratification by the states. The amendment outlawed only the manufacture, sale, and transport of liquor, not the possession of alcohol for personal use. It did not make buying liquor from bootleggers (people who produced alcohol illegally) a crime.

To carry out the intent of the amendment, Congress passed the National Prohibition Act, better known as the Volstead Act. The Volstead Act allowed supplies of alcohol to be produced and transported for scientific and other commercial purposes. It also defined an intoxicating liquor as any beverage containing more than 0.5 percent alcohol. It could have set the permissible level higher to allow the production, transportation, and sale of beer, but it did...