Which amendment to the US Constitution launched Prohibition in 1920 by banning the sale of alcoholic beverages?

The Eighteenth Amendment launched national Prohibition in 1920 by prohibiting the manufacture, sale and transportation of intoxicating liquor in the United States.

Congress proposed the amendment in December 1917, after decades of campaigning by temperance organizations, Protestant reformers and other groups that blamed alcohol for poverty, domestic violence and social disorder. It was ratified by the required three-quarters of the states on 16 January 1919, but took effect one year later, on 17 January 1920.

The amendment itself established the constitutional ban, while the Volstead Act supplied the legal definitions and enforcement framework. Prohibition did not make every relationship with alcohol illegal: possession and consumption were not directly banned by the amendment, and alcohol could still be used in limited medical and religious contexts.

The amendment was repealed in 1933 by the Twenty-first Amendment, making it the only US constitutional amendment ever repealed in full. A frequent mix-up is reversing the Eighteenth and Twenty-first Amendments: the former began Prohibition, while the latter ended it.