The U.S. Supreme Court's ruling in Plessy v. Ferguson (1896) was significant because it upheld racial segregation under the “separate but equal” doctrine. This landmark decision legitimized state laws that mandated segregation in public facilities, effectively enshrining racial discrimination in American society. Plessy challenged Louisiana’s segregation laws after being arrested for sitting in a “whites-only” railway car. The ruling reinforced the legal basis for Jim Crow laws in the South, exacerbating racial tensions and institutional inequality for decades. It wasn’t until the Brown v. Board of Education decision in 1954 that Plessy was ultimately overturned, advancing civil rights efforts.