On July 1, 1870, the United States Department of Justice formally came into existence. The Department of Justice (DOJ) is the United States federal department responsible for the enforcement of the law and administration of justice, and is led by the Attorney General.

The Attorney General position was established in 1789 as a one-person, part-time job, but as the country and the government grew, so did the position. In 1867, the U.S. House Committee on the Judiciary conducted an inquiry into the creation of a “law department” headed by the Attorney General and composed of United States attorneys. In February of 1868, Congressman William Lawrence introduced a bill in Congress to create the Department of Justice. However, this first bill was unsuccessful.

A second bill was introduced to Congress by Rhode Island Representative Thomas Jenckes in February of 1870. The bill, called the Act to Establish the Department of Justice, did little to change the Attorney General's responsibilities, but did create a new office, the Solicitor General, who was to supervise and conduct government litigation in the Supreme Court of the United States. Both the Senate and House passed the bill rather quickly, and President Ulysses S. Grant then signed the bill into law on June 22, 1870. The Department of Justice officially began operations on July 1, 1870.

Today, the DOJ is headquartered at the Robert F. Kennedy Department of Justice Building in Washington, D.C. The DOJ oversees the administration of several agencies, including the Federal Bureau of Investigation, the Bureau of Alcohol, Tobacco, Firearms, and Explosives, and the Drug Enforcement Administration.