On July 26, 1908, the Federal Bureau of Investigation (FBI) is born when U.S. Attorney General Charles Bonaparte orders a group of newly hired federal investigators to report to Chief Examiner Stanley W. Finch of the Department of Justice. One year later, the Office of the Chief Examiner was renamed the Bureau of Investigation, and in 1935 it became the Federal Bureau of Investigation.
When the Department of Justice was created in 1870 to enforce federal law and coordinate judicial policy, it had no permanent investigators on its staff. At first, it hired private detectives when it needed federal crimes investigated and later rented out investigators from other federal agencies, such as the Secret Service, which was created by the Department of the Treasury in 1865 to investigate counterfeiting. In the early part of the 20th century, the attorney general was authorized to hire a few permanent investigators, and the Office of the Chief Examiner, which consisted mostly of accountants, was created to review financial transactions of the federal courts.
Seeking to form an independent and more efficient investigative arm, in 1908 the Department of Justice hired 10 former Secret Service employees to join an expanded Office of the Chief Examiner. The date when these agents reported to duty–July 26, 1908–is celebrated as the genesis of the FBI. By March 1909, the force included 34 agents, and Attorney General George Wickersham, Bonaparte’s successor, renamed it the Bureau of Investigation.
Source: The History Channel