Which landmark Supreme Court case established the principle of "separate but equal"?

The principle of "separate but equal" was established in the Supreme Court case of Plessy v. Ferguson in 1896. This case involved Homer Plessy, who challenged Louisiana's segregation laws by sitting in a whites-only railroad car. The Supreme Court upheld the state's segregation laws, asserting that racially separated facilities for African Americans and whites were constitutional as long as they were equal in quality. This decision provided legal justification for racial segregation across various public facilities and services, cementing the practice in American society for many years.

The significance of Plessy v. Ferguson lies in its long-lasting impact on the legal framework supporting racial discrimination, which was only overturned by later cases, including Brown v. Board of Education in 1954, which declared that segregation in public schools was inherently unequal and unconstitutional.