January 1919 brought the crowning achievement of the Temperance movement: the United States was voted dry. The 18th Amendment to the United States Constitution, which prohibited the manufacture, sale, or transportation of intoxicating liquors in the United States, was ratified by 46 states; only Connecticut and Rhode Island rejected the amendment. By the terms of the amendment, it was slated to go into effect one year after ratification, which allowed time for development of appropriate legislation for enforcement.
Later that year, the National Prohibition Act (also called the Volstead Act) expanded on the 18th Amendment and the previously enacted War Prohibition Act by specifying strength of alcohol that was prohibited, penalties for lawbreaking, and exceptions that could be made for medicine, religious rituals, and scientific research. Neither law actually prohibited the consumption of alcohol for enjoyment, but they made it more difficult to obtain legally.
The 18th Amendment was repealed in 1933 by the 21st Amendment; to this day, it is the only constitutional amendment to be repealed in its entirety.