In Marbury v. Madison (1803), the Supreme Court established the principle of judicial review by ruling that a section of the Judiciary Act of 1789 was unconstitutional. This allowed the Court to determine the constitutionality of laws and assert its role as an equal branch of government. In McCulloch v. Maryland (1819), the Court upheld the constitutionality of the national bank and established Congress's implied powers under the Necessary and Proper Clause, expanding federal power. In Plessy v. Ferguson (1896), the Court endorsed the doctrine of "separate but equal" and allowed states to require racial segregation as long as facilities were equal, legalizing racial discrimination for over 50 years.