What was key to the Supreme Court's argument in the verdict of the 1896 Plessy v. Ferguson case?

The key argument in the Supreme Court's verdict in the 1896 Plessy v. Ferguson case was the concept of "separate but equal." The Court held that racially segregated public facilities did not violate the Equal Protection Clause of the Fourteenth Amendment as long as the facilities were equal in quality. This legal doctrine legalized racial segregation in public places, paving the way for Jim Crow laws and institutionalized racial discrimination in the United States for several decades.