Its investigators were called "Prohibition Agents," or more colloquially "prohis." Its most famous agent was Eliot Ness. Some of the other famous lawmen who carried a "Prohi's" badge at one time of another in their career include former Texas Ranger Frank Hamer, full-blooded Cherokee Tom Threepersons, and Chicagoan Pat Roche. The two-agent team of Isidor "Izzy" Einstein and Moe Smith, working out of the New York City office, compiled the best arrest record in the history of the agency.
On July 1, 1930, the Prohibition Bureau was transferred from the Treasury Department to the Department of Justice. Early in 1933, as part of the Franklin D. Roosevelt-sponsored "Omnibus Crime Bill," the Prohibition Bureau was briefly absorbed into the Federal Bureau of Investigation (FBI), or "Division of Investigation" as the agency was then called. At this point it became the "Alcohol Beverage Unit." Though part of the FBI on paper, J. Edgar Hoover, who wanted to avoid liquor enforcement and the taint of corruption that was attached to it, continued to operate it as a separate, autonomous agency in practice.
Following the repeal of Prohibition in December 1933, the Alcohol Beverage Unit was removed from the FBI and the Justice Department, and returned to Treasury, where, coming full circle, it became the Alcohol Tax Unit of the IRS, ultimately evolving into the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).