On July 1, 1870, the US Congress’s “Act to Establish the Department of Justice” took effect, and the US Department of Justice (DOJ) was officially founded. The Act took the existing office of the Attorney General and made it the head of the new executive department. Congress created the department due to the ongoing legal difficulties surrounding Reconstruction following the US Civil War, the process where the states in rebellion were formally readmitted to the Union and emancipated slaves gained citizenship for the first time.
Learn more from the Department Of Justice.