Prohibition was important in the 1920s because it demonstrated that banning something can have the opposite effect of making it more desirable and more dangerous. By banning alcohol, many people started making their own homemade versions, sometimes with poisonous ingredients. Prohibition also saw the rise of organized crime associated with bootlegging.
Prohibition began in 1920, a year after the 18th Amendment banning alcohol was ratified on January 29, 1919. While at first it resulted in a 30 percent drop in alcohol consumption and a decline in alcohol-related arrests, over time both crime and alcoholism increased as people found ways to get around the laws. In December, 1933, the 21st Amendment was ratified and repealed the 18th, ending Prohibition.