Today, the FBI is famously known throughout the world as the chief investigative unit of the United States government. It operates as a division of the Department of Justice to "protect and defend the United States against terrorist and foreign intelligence threats, to uphold and enforce the criminal laws of the United States, and to provide leadership and criminal justice services to federal, state, municipal, and international agencies and partners."
When it was first conceived in 1908, the department had no name. It was referred to as a "special agent force" or a "corps of special agents." It was officially designated as the Bureau of Investigation (BOI) on March 16, 1909. Only later, in 1935, less than two years after the end of prohibition, did it become the Federal Bureau of Investigation, or FBI.
The case files in this publication group are from the early days of the Bureau of Investigation. They cover changes in interstate commerce and foreign affairs during the Progressive Era of President Theodore Roosevelt. When the United States entered World War I, agents investigated espionage, sabotage, and other threats to a nation in wartime. The 18th amendment instituted prohibition in 1920 and gangsterism and similar lawlessness occupied many of the Bureau's resources. J. Edgar Hoover started working at the BOI in 1917, was named assistant director in 1921, and began his 48-year career as director of the BOI and FBI in 1924.
Case files in the BOI series are divided into four distinct groups:
Bureau Section Files, 1920-21 These records consist of investigative reports and correspondence from other areas of the Department of Justice whose investigative functions were later absorbed by the BOI. Many are duplicated in Miscellaneous Files.
Mexican Files, 1909-21 These are records relating to Mexican neutrality violations. They are arranged numerically, with numbers beginning with #232-. They cover investigations of conditions on the Mexican border beginning in 1916, including investigations of people operating against US interests during the Mexican civil wars.
Miscellaneous Files, 1908-22 Files are arranged by file numbers, corresponding to dates on which investigations were initiated. They contain investigative reports, correspondence, and memos dealing with alleged violations of federal laws.
Old German Files, 1915-20 By far the largest group of files, these are investigative records relating to German aliens who were politically suspect before and during World War I, more specifically, in the period 1915-20. Case numbers for these files begin with #8000- and comprise nearly 400,000 records. Explore the case of German terrorist Werner Horne and view images from his file below.
_More information about the entire collection can be found in NARA's descriptive pamphlet _M1085.