Final answer:
The 18th Amendment was repealed by the 21st Amendment due to its unpopularity and enforcement difficulties.
Step-by-step explanation:
The Eighteenth Amendment, which banned the sale of alcohol in the United States, was repealed by the passage of the Twenty First Amendment. The 18th Amendment faced many problems and was largely unpopular. The enforcement of the ban on alcohol was difficult and led to an increase in organized crime and illegal activities. The public sentiment turned against prohibition, and the 21st Amendment was passed to repeal the 18th Amendment, effectively ending Prohibition in 1933.