John Marshall was an influential American statesman and jurist who served as the fourth Chief Justice of the United States from 1801 to 1835. He played a crucial role in establishing the principles of American constitutional law and is known for his strong support of federal authority. His decisions helped shape the balance of power between the federal government and the states. Marshall's most notable case was Marbury v. Madison in 1803, which established the principle of judicial review, allowing the Supreme Court to invalidate laws that conflict with the Constitution. His tenure significantly impacted the development of the American legal system and the role of the judiciary.