Conversation so far:
What are the most important US supreme court cases?
Marbury v. Madison, 1803 (4-0 decision) ...McCulloch v. Maryland, 1819 (7-0 decision) ...Dred Scott v. Sandford, 1857 (7-2 decision) ...Plessy v. Ferguson, 1896 (7-1 decision) ...Korematsu v. United States,

Question: What did Plessy v. Ferguson establish?
Self-contained rewrite: What did Plessy v. Ferguson establish?