Plessy v. Ferguson was a landmark United States Supreme Court case decided in 1896. The case involved an African American man named Homer Plessy who intentionally violated a Louisiana state law by sitting in a "whites-only" railroad car. Plessy was arrested and found guilty of breaking the law, leading to his appeal to the Supreme Court.

In a 7-1 decision, the Supreme Court upheld the constitutionality of racial segregation laws for public facilities as long as the facilities were considered "separate but equal." This ruling established the legal doctrine of "separate but equal," which allowed for segregation in public facilities such as schools, transportation, and other public spaces. This decision essentially legalized racial segregation and discrimination in the United States for decades to come.

Plessy v. Ferguson was a significant blow to the civil rights movement, setting the stage for further institutionalized racism and discrimination against African Americans. It wasn't until the landmark case of Brown v. Board of Education in 1954 that the "separate but equal" doctrine was overturned, marking a major victory in the fight for civil rights and desegregation in the United States.