The creation of the United States Department of Justice marked a significant moment in the development of federal authority over legal matters in the post-Civil War era. Established on July 1, 1870, through a bill sponsored by Congressman John A. Bingham and signed into law by President Ulysses S. Grant, the Department aimed to provide a coordinated approach to federal law enforcement. Prior to this establishment, legal enforcement was fragmented, lacking a cohesive strategy to combat crime and ensure justice across states. This was particularly pertinent after the Civil War when the nation faced numerous legal challenges, particularly in the Southern states where lawlessness was rampant.

The primary responsibilities of the Department include overseeing federal prosecutions, providing legal advice to the president, and representing the United States in legal matters. The Attorney General, who heads the department, became a crucial figure in shaping federal law enforcement policy. The establishment of the Department of Justice represented a commitment to upholding the rule of law and protecting civil rights, especially during a time of great social upheaval in America.

As the role of the Department evolved, it took on additional responsibilities, including civil rights enforcement, antitrust scrutiny, and handling immigration cases. The early years saw the Department navigating a landscape marked by challenges, such as the enforcement of Reconstruction-era laws designed to protect former slaves and combat discriminatory practices. Over time, the Department's mandate expanded, influencing various aspects of American society, including labor laws, civil rights protections, and environmental regulations.