From Wiki:
The ATF was formerly part of the United States Department of the Treasury, having been formed in 1886 as the "Revenue Laboratory" within the Treasury Department's Bureau of Internal Revenue. The history of ATF can be subsequently traced to the time of the revenuers or "revenoors"[7] and the Bureau of Prohibition, which was formed as a unit of the Bureau of Internal Revenue in 1920. It was made an independent agency within the Treasury Department in 1927, was transferred to the Justice Department in 1930, and became, briefly, a division of the FBI in 1933.
When the Volstead Act, which established Prohibition in the United States, was repealed in December 1933, the Unit was transferred from the Department of Justice back to the Department of the Treasury where it became the Alcohol Tax Unit (ATU) of the Bureau of Internal Revenue. Special Agent Eliot Ness and several members of The "Untouchables", who had worked for the Prohibition Bureau while the Volstead Act was still in force, were transferred to the ATU. In 1942, responsibility for enforcing federal firearms laws was given to the ATU.
In the early 1950s, the Bureau of Internal Revenue was renamed "Internal Revenue Service" (IRS),[8] and the ATU was given the additional responsibility of enforcing federal tobacco tax laws. At this time, the name of the ATU was changed to the Alcohol and Tobacco Tax Division (ATTD).
In 1968, with the passage of the Gun Control Act, the agency changed its name again, this time to the Alcohol, Tobacco, and Firearms Division of the IRS and first began to be referred to by the initials "ATF". In Title XI of the Organized Crime Control Act of 1970, Congress enacted the Explosives Control Act, 18 U.S.C.A. Chapter 40, which provided for close regulation of the explosives industry and designated certain arsons and bombings as federal crimes. The Secretary of the Treasury was made responsible for administering the regulatory aspects of the new law, and was given jurisdiction over criminal violations relating to the regulatory controls. These responsibilities were delegated to the ATF division of the IRS. The Secretary and the Attorney General were given concurrent jurisdiction over arson and bombing offenses. Pub.L. 91-452, 84 Stat. 922, October 15, 1970.
In 1972 ATF was established as a separate bureau within the Treasury Department when Treasury Department Order 221, effective July 1, 1972, transferred the responsibilities of the ATF division of the IRS to the new Bureau of Alcohol, Tobacco, and Firearms.
That’s what I was talking g about. I was about to post a link and saw Elderberry already had.