National Beer Day is celebrated in the United States every year on April 7, marking the day that the CullenHarrison Act came into force after having been signed into law by President Franklin D. Roosevelt on March 22, 1933. This led to the Eighteenth Amendment being repealed on December 5, 1933, with the ratification of the Twenty-first Amendment to the U.S. Constitution. April 6, the day prior to National Beer Day, is known as New Beer's Eve.

Prohibition in the United States was a nationwide constitutional ban on the production, importation, transportation, and sale of alcoholic beverages from 1920 to 1933.Prohibitionists first attempted to end the trade in alcoholic drinks during the 19th century. Led by pietistic Protestants, they aimed to heal what they saw as an ill society beset by alcohol-related problems such as alcoholism, family violence and saloon-based political corruption. Many communities introduced alcohol bans in the late 19th and early 20th centuries, and enforcement of these new prohibition laws became a topic of debate. Prohibition supporters, called "drys", presented it as a battle for public morals and health. The movement was taken up by progressives in the Prohibition, Democratic and Republican parties, and gained a national grassroots base through the Woman's Christian Temperance Union. After 1900, it was coordinated by the Anti-Saloon League. Opposition from the beer industry mobilized "wet" supporters from the wealthy Catholic and German Lutheran communities, but the influence of these groups receded from 1917 following the entry of the U.S. into the First World War against Germany.

The alcohol industry was curtailed by a succession of state legislatures, and finally ended nationwide under the Eighteenth Amendment to the United States Constitution, ratified in 1919, which passed "with a 68 percent supermajority in the House of Representatives and 76 percent support in the Senate" as well as ratification by 46 out of 48 states. Enabling legislation, known as the Volstead Act, set down the rules for enforcing the federal ban and defined the types of alcoholic beverages that were prohibited. Not all alcohol was banned; for example, religious use of wine was permitted. Private ownership and consumption of alcohol were not made illegal under federal law, but local laws were stricter in many areas, with some states banning possession outright.

Following the ban, criminal gangs gained control of the beer and liquor supply in many cities. By the late 1920s, a new opposition to Prohibition emerged nationwide. Critics attacked the policy as causing crime, lowering local revenues, and imposing "rural" Protestant religious values on "urban" America. Prohibition ended with the ratification of the Twenty-first Amendment, which repealed the Eighteenth Amendment on December 5, 1933, though prohibition continued in some states. To date, this is the only time in American history in which a constitutional amendment was passed for the purpose of repealing another.

Some research indicates that alcohol consumption declined substantially due to Prohibition. Rates of liver cirrhosis, alcoholic psychosis, and infant mortality also declined. Prohibition's effect on rates of crime and violence is disputed. Despite this, it lost supporters every year it was in action, and lowered government tax revenues at a critical time before and during the Great Depression.