What 3 words provided the legal basis for segregation in America

"Separate but equal" are the three words that stood as the legal basis for segregation in America. This concept was established in the Supreme Court case Plessy vs. Ferguson in 1896. This case ruled that having "separate but equal" facilities was not a violation of the 14th amendment. This ruling changed American society for the next 6 decades. Public schools and transportation remained segregated. It was not until the Brown vs. Board of Education case overruled this concept and deemed "separate but equal" unconstitutional.