In 1948, the agency’s preparation of a 123-page amicus brief in Shelley v. Kraemer and Hurd v. Hodge—which challenged courts' enforcement of racially restrictive deed covenants that were used to create and maintain whites-only neighborhoods—marked the beginning of the agency's unofficial partnership with the NAACP. In Henderson v. United States (1949), the agency challenged the longstanding legality of providing "separate-but-equal" facilities for African Americans, leading DOJ to make the same argument in Brown v. Board of Education and the DC companion case Bolling v. Sharpe. In Brown, the Supreme Court finally overturned the 1896 ruling in Plessy v. Ferguson that had upheld the provision of separate transportation, schools, and other public accommodations for African Americans. Segregated schools violated the 5th and 14th amendments, said the Court.
Established in 1957, DOJ's Civil Rights Division was initially charged with defending black voting rights in the South, especially after the Supreme Court ruled in 1960 that gerrymandering—the adjustment of voting district boundaries to suppress the influence of black voters—violated the 15th Amendment. (Protecting black voting rights had been the reason for DOJ's establishment in 1870.) After the passage of the 1965 Voting Rights Act, the Division helped eliminate literacy tests and other barriers to black voting. It also worked to enforce court orders mandating the desegregation of universities (Division Director John Doar escorted James Meredith onto the University of Mississippi's campus in 1962); to desegregate interstate travel as required by the 1964 Civil Rights Act; and to investigate racially targeted violence, including the 1963 bombing of the 16th Street Baptist Church in Birmingham, Alabama, and the 1965 murders in Alabama of Viola Liuzzo and Rev. James Reeb.
In the 1990s, the Division's investigation of black church burnings resulted in hundreds of arrests. Following the brutal beating by Los Angeles police of Rodney King in 1991, DOJ was charged with investigating and overseeing police departments across the country, including in DC.
The FBI, which is part of DOJ, essentially endorsed racial violence in the South until the 1960s by neglecting to prevent or investigate lynchings, debt peonage, police terror, voter suppression, and other tools of maintaining white supremacy. The FBI also wiretapped the Rev. Dr. Martin Luther King, Jr. and his colleagues, and used undercover surveillance to track individuals and groups such as A. Philip Randolph, Julius Hobson, the NAACP, the National Negro Congress, and the Student Nonviolent Coordinating Committee (SNCC).