The landmark court case that ruled against segregation in public schools in Washington, D.C., was Brown v. Board of Education in 1954. This unanimous decision by the Supreme Court declared that racial segregation in public schools violated the Equal Protection Clause of the 14th Amendment. The ruling overturned the precedent set by Plessy v. Ferguson, which upheld the "separate but equal" doctrine. The Brown case was a significant milestone in the Civil Rights Movement, sparking further legal and social challenges to segregation throughout the United States and advancing the cause of racial equality.