Prohibition in the United States

The Prohibition Era was a period in United States history when alcohol was outlawed. Police would arrest anyone who was found making or selling alcohol illegally. The Women's Christian Temperance Union and other reformist organizations agitated for this change in order to improve the lives of the people. Prohibition lasted from 1920 to 1933. It was established by the Eighteenth Amendment to the United States Constitution. It was ratified (approved by the states) by January 16, 1919. It came into effect at January 16, 1920. 
The punishment for being caught with an alcoholic beverage was jail time. The millions of people becoming criminals in such a short period of time led to overflowing prisons and it was common to have a case dismissed. Prohibition was a constitutional experiment set up by the American government in an effort to decrease crime rates, reduce tax burden, and improve health in Americans. It had little to do with the consumption of alcoholic beverages.
Prohibition was good as the consumption of alcohol was reduced, but it was bad in that the Mafia and other underground organizations took up rum-running. They became big and powerful and made trouble. Prohibition was repealed December 5, 1933 by the Twenty-first Amendment. Now states can regulate the selling of liquor by themselves.
Due to the demand of alcohol, illegal pubs were built called speakeasies.These could be in the form of a proper pub or just in someones basement.