The Lever Food and Fuel Control Act of August 1917 banned the production of distilled spirits for the duration of the war. The War Prohibition Act of November 1918 forbade the manufacture and sale of all intoxicating beverages of more than 2.75 percent alcohol content, beer and wine as well as hard liquor, until demobilization was completed.
The 18th amendment, BTW, was ratified January 16, 1919.