Plessy v. Ferguson was a landmark Supreme Court case decided in 1896. It involved Homer Plessy, a man of mixed race who challenged Louisiana's segregation laws after being arrested for sitting in a "whites-only" train car. The Court ruled that racial segregation was constitutional under the "separate but equal" doctrine, which allowed for separate facilities for different races as long as they were considered equal. This decision upheld state laws that enforced racial segregation and legitimized discriminatory practices across the United States. The ruling remained in effect until it was eventually overturned by Brown v. Board of Education in 1954, which declared that separate educational facilities were inherently unequal.