Final answer:
The Plessy v. Ferguson case focused on the equal protection clause of the Fourteenth Amendment and established the concept of 'separate but equal'.
Step-by-step explanation:
The landmark Supreme Court case Plessy v. Ferguson focused on the equal protection clause of the Fourteenth Amendment. In this case, Homer Plessy challenged a Louisiana law that required racial segregation of railroad cars. Despite arguing that the law violated the principle of equal protection, the Supreme Court ruled that the law was not a violation and established the concept of 'separate but equal'.