The office of the attorney general was established by the Judiciary Act of 1789 as a part-time job for one person, but grew with the bureaucracy.

Their main function was to generate legal opinions at the request of Lincoln and cabinet members, and handle occasional cases before the Supreme Court.

Bates did have an opportunity to comment on general policy as a cabinet member with a strong political base, but he seldom spoke up.

[9] Both Akerman and Bristow used the Department of Justice to vigorously prosecute Ku Klux Klan members in the early 1870s.

By 1871, there were 3000 indictments and 600 convictions, with most only serving brief sentences, while the ringleaders were imprisoned for up to five years in the federal penitentiary in Albany, New York.

[10] George H. Williams, who succeeded Akerman in December 1871, continued to prosecute the Klan throughout 1872 until the spring of 1873, during Grant's second term in office.

[12] The law also created the office of Solicitor General to supervise and conduct government litigation in the Supreme Court of the United States.

[13] With the passage of the Interstate Commerce Act in 1887, the federal government took on some law enforcement responsibilities, and the Department of Justice was tasked with performing these.

[15] In 1933, President Franklin D. Roosevelt issued an executive order which gave the Department of Justice responsibility for the "functions of prosecuting in the courts of the United States claims and demands by, and offsenses [sic] against, the Government of the United States, and of defending claims and demands against the Government, and of supervising the work of United States attorneys, marshals, and clerks in connection therewith, now exercised by any agency or officer..."[16] The U.S. Department of Justice building was completed in 1935 from a design by Milton Bennett Medary.

On a lot bordered by Constitution and Pennsylvania Avenues and Ninth and Tenth Streets, Northwest, it holds over 1,000,000 square feet (93,000 m2) of space.

It was criticized by government watchdog groups for its alleged violation of U.S. Code Title 18 Section 1913, which forbids money appropriated by Congress to be used to lobby in favor of any law, actual or proposed.

On October 5, 2021, U.S. Deputy Attorney General Lisa Monaco has announced the formation of a "Cryptocurrency Enforcement Team" during the Aspen Cyber Summit.