Enforcement of Prohibition was difficult and ultimately ineffective. Enforcement was initially largely delegated to state and local police. On the federal level, the Prohibition Unit (later called the Bureau of Prohibition) was established within the Bureau of Internal Revenue. The unit was later moved to the Treasury Department and then Department of Justice, ultimately evolving into today’s Bureau of Alcohol, Tobacco, and Firearms (ATF). The demand for alcohol was high, and organized crime gangs grew wealthy and powerful in meeting that demand, importing alcohol from other countries and establishing illegal bars (“speakeasies”) to sell it.
Enforcement methods included setting up fake speakeasies, tapping phone lines, and executing raids. Illegal alcohol sale was so profitable that even with raids and arrests by law enforcement, speakeasies and other illegal activity thrived. Corruption was also rampant, further complicating enforcement efforts and making convictions after arrest relatively rare.