Which Supreme Court case affirmed the "separate but equal" doctrine before the Civil Rights Movement challenged it?

The "separate but equal" doctrine was affirmed in the Plessy v. Ferguson case in 1896. This Supreme Court decision upheld state laws that established racial segregation in public facilities, under the premise that if the separate facilities for the races were equal, then segregation did not violate the Equal Protection Clause of the Fourteenth Amendment. This ruling provided legal justification for racial segregation and discrimination, essentially codifying the segregationist policies that would dominate the United States until the Civil Rights Movement began to challenge them significantly in the mid-20th century.

The significance of this case lies in how it entrenched the notion of racial separation into American law and societal norms, paving the way for systemic discrimination. It wasn't until the landmark decision in Brown v. Board of Education in 1954 that the "separate but equal" doctrine was overturned, marking a significant turning point in the fight for civil rights.