The Judiciary Act of 1789, ch. 20, sec. 35, 1 Stat. 73, 92-93 (1789) created the Office of the Attorney General. Originally a one-person part-time position, the Attorney General was to be "learned in the law" with the duty "to prosecute and conduct all suits in the Supreme Court in which the United States shall be concerned, and to give his advice and opinion upon questions of law when required by the President of the United States, or when requested by the heads of any of the departments, touching any matters that may concern their departments." The workload quickly became too much for one person, necessitating the hiring of several assistants for the Attorney General. With an increasing amount of work to be done, private attorneys were retained to work on cases.
In 1870, after the post-Civil War increase in the amount of litigation involving the United States necessitated the very expensive retention of a large number of private attorneys to handle the workload, a concerned Congress passed the Act to Establish the Department of Justice, ch. 150, 16 Stat. 162 (1870) setting it up as "an executive department of the government of the United States" with the Attorney General as its head. Officially coming into existence on July 1, 1870, the Department of Justice, pursuant to the 1870 Act, was to handle the legal business of the United States. The Act gave the Department control over all criminal prosecutions and civil suits in which the United States had an interest. In addition, the Act gave the Attorney General and the Department control over federal law enforcement. To assist the Attorney General, the 1870 Act created the Office of the Solicitor General.
The 1870 Act is the foundation upon which the Department of Justice still rests. However, the structure of the Department of Justice has changed over the years, with the addition of the Deputy Attorneys General and the formation of the Divisions. Unchanged is the steadily increasing workload of the Department. It has become the world's largest law office and the central agency for enforcement of federal laws.