Which amendment allowed alchaol to be sold again and why?

18th and amendment 

By the late 1800s, prohibition movements had sprung up across the United States, driven by religious groups who considered alcohol, specifically drunkenness, a threat to the nation. The movement reached its apex in 1920 when Congress ratified the 18th Amendment, prohibiting the manufacture, transportation and sale of intoxicating liquors. Prohibition proved difficult to enforce and failed to have the intended effect of eliminating crime and other social problems–to the contrary, it led to a rise in organized crime, as the bootlegging of alcohol became an ever-more lucrative operation. In 1933, widespread public disillusionment led Congress to ratify the 21st Amendment, which repealed Prohibition.