The National Prohibition Act, known informally as the Volstead Act, was an act of the 66th United States Congress designed to execute the 18th Amendment which established the prohibition of alcoholic drinks. The Anti-Saloon League's Wayne Wheeler conceived and drafted the bill, which was named after Andrew Volstead, chairman of the House Judiciary Committee, who managed the legislation.

The 66th United States Congress was a meeting of the legislative branch of the United States federal government, comprising the United States Senate and the United States House of Representatives. It met in Washington, D.C., from March 4, 1919, to March 4, 1921, during the last two years of Woodrow Wilson's presidency. The apportionment of seats in the House of Representatives was based on the 1910 United States census.