Elliot Ness and his men go on a liquor raid during prohibiton. He surprised to learn the alcohol is being stored at a Post Office but his partner informs him of the open nature of alochol smuggling in Chicago during the time.
The Prohibition of Alcohol in the 1920s had a lot of problems, including the general poor public opinions involving it and the creation of organized crime syndicates who profited off selling the new illegal items