The 18th Amendment goes into effect, starting Prohibition and leading to the rise of illegal alcohol trade, an important backdrop for Boardwalk Empire.
The U.S. government establishes the Bureau of Prohibition to enforce the new laws against alcohol manufacture and sale, impacting the criminal enterprises depicted in Boardwalk Empire.
Al Capone becomes one of the most notorious gangsters of the Prohibition era, influencing the organized crime activities shown in Boardwalk Empire.
Prohibition ends with the repeal of the 18th Amendment, changing the dynamics of organized crime and politics as portrayed in Boardwalk Empire.