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 by sitting in a "whites-only" train car. The Court ruled that racial segregation was constitutional under the "separate but equal" doctrine, meaning that as long as facilities for both races were equal, segregation did not violate the 14th Amendment. This decision upheld state laws that enforced racial segregation and legitimized discriminatory practices across the United States. It remained in effect until it was overturned by the Brown v. Board of Education decision in 1954, which declared that separate educational facilities were inherently unequal.