The landmark Supreme Court case that upheld segregation laws in the United States was Plessy v. Ferguson, decided in 1896. The Court ruled that racial segregation was constitutional under the doctrine of “separate but equal”. This decision provided a legal foundation for segregation laws, particularly in the South, legitimizing discrimination against African Americans and leading to the proliferation of Jim Crow laws. Plessy v. Ferguson remained a critical precedent until it was finally overturned by Brown v. Board of Education in 1954, which declared segregated public schools unconstitutional.