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. 