A Twentieth-Century Genealogical Resource: FBI Records


The Federal Bureau of Investigation (FBI) serves as the nation’s federal law enforcement agency, and as an intelligence, security, and investigative organization. Established in 1908 as the Bureau of Investigation, the agency was known as the United States Bureau of Investigation and the Division of Investigation before it became known as the Federal Bureau of Investigation in 1935.

The majority of FBI records are investigative case files, although other types of records are also available to researchers. Investigative case files begin in the early twentieth century, and are related to a variety of topics including prohibition, the Selective Service Act, passport matters, civil rights, espionage, treason, corruption, kidnapping, terrorism, background investigations, foreign counterintelligence, and various federal crimes.

Investigative case files are different in scope, size, and content, but can include details about a person’s life, family members, education, employment, associates, and activities. Many files include observations about the subject, and results of interviews and interrogations. The files can provide information about witnesses, associates, and family members of the person being investigated. Investigative case files exist for both individuals and organizations. Some FBI records have been released to the public, while others are available solely by request through the Freedom of Information Act (FOIA).

Investigative Files: 1908-1922
Investigative files covering the period of 1908 through 1922 have been transferred to the National Archives and Records Administration (NARA) and are part of Record Group (RG) 65, Records of the Federal Bureau of Investigation. These case files and a name index are part of NARA microfilm publication M1085, Investigative Case Files of the Bureau of Investigation, 19081922, available at the National Archives in Washington, D.C., and digitally via Fold3. A descriptive pamphlet for this series is also available.

The investigative case files are separated into four categories: “Miscellaneous,” “Old German,” “Mexican,” and “Bureau Section” files. They include reports, correspondence, and other records covering a wide range of topics. The “Miscellaneous” files include general investigative reports and correspondence related to violations of federal laws. The “Old German” files, covering from 1915 to 1920, are related to investigations of German aliens and sympathizers during the World War I period. While many of these files are related to Germans, individuals of other nationalities were also investigated and are represented in the records. The “Mexican” files are investigative records related to Mexican Neutrality Violations between 1909 and 1921, including investigations of conditions on the Mexican border. The “Bureau Section Files” cover 1920 to 1921, and consist of reports and correspondence transferred from the Department of Justice to the FBI. These files, which include many immigration and citizenship matters, and investigations into men who did not register for the World War I draft, can include significant genealogical information.

In addition to the FBI, other federal government agencies conducted various types of investigations. Records of those investigations, as well as agency correspondence and other record types, can be found in several NARA record groups, including RG 59, General Records of the Department of State; RG 60, Records of the Department of Justice; RG 85, Records of the Immigration and Naturalization Service; RG 87, Records of the Secret Service; and RG 165, Records of the War Department General and Special Staffs.

General FBI Records
In addition to investigative case files, other records that are part of NARA RG 65 may be of interest to genealogists, including:

  • Records of the American Protective League, a volunteer organization that assisted federal agencies by conducting investigations, providing information about disloyal persons, and locating Selective Service Act delinquents. These records cover the period of 1917 to 1919, and include investigation requests, member registers, member records, and the organization’s newsletter.
  • Records of the National Bureau of Criminal Identification, which was responsible for compiling criminal identification records to share with law enforcement agencies. These records include correspondence, criminology pamphlets, criminal identification cards, fingerprint registers (with an index), photographs of known criminals, and other miscellaneous records covering the period of 1897 to 1924.
  • Administrative records, including appointment applications, personnel files, correspondence concerning cases and special agents, scrapbooks, and memorabilia.

Investigative Files: Post-1922
In 1921, the FBI established the Central Records System to organize investigative case files. Beginning in 1922, records were arranged using a numerical classification system. The first part of every record’s identification number includes three digits that correspond to a set classification number for the offense or matter being investigated. For example, prohibition matters began with the number 023, and violations of the Selective Service Act began with the number 025. The FBI’s present classification list can be found here. The second part of the record number is the case file number within that classification, followed by a unique number for each document within that case file.

Some post-1922 records are still with the FBI, and others have been transferred to NARA but not made publicly available. Requests for post-1922 FBI case files must be made through a FOIA request, and should include the name or names of the subject of the investigation, their dates and places of birth and death, proof of death for individuals born less than 100 years ago, the requestor’s full name and address, and the reason for the request. (See a sample request letter here.) Requests may be sent via email to foiparequest@ic.fbi.gov; via fax to (540) 868-4391 or (540) 868-4997; or via mail to FBI, Record/Information Dissemination Section, Attn: FOIPA Request, 170 Marcel Drive, Winchester, VA 22602-4843.

Processing time varies by the size of the file being requested. Some researchers may receive follow-up correspondence regarding file size and reproduction costs. All requests will result in either a response to inform the requestor that no records have been found, or a case file and a letter explaining any exceptions to the request. Classified or private information may be redacted from the case file.

Records and Indexes
Some records that have previously been requested through FOIA and released to the public are available through the FBI Vault. This digital library includes a database that can be searched by topic or name, and an alphabetical listing that can be browsed by topic or name. The search function allows for keyword searches within files. Additionally, an index to FBI investigative case files related to the Nazi War Crimes and Japanese Imperial Government Disclosure Acts is available at the National Archives and online.

The Federal Bureau of Investigation’s case files and administrative records can be a valuable resource for genealogists researching twentieth-century ancestors. For more information, visit the NARA RG 65 page and the Requesting FBI Records page.

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