John Marshall (1755 – 1835) was the fourth Chief Justice of the United States (1801–1835), whose court opinions helped lay the basis for American constitutional law and made the Supreme Court of the United States a coequal branch of government along with the legislative and executive branches. Previously, Marshall had been a leader of the Federalist Party in Virginia, served in the United States House of Representatives, and was Secretary of State under President John Adams from 1800 to 1801.
The longest-serving Chief Justice, Marshall dominated the Court for over three decades and played a significant role in the development of the American legal system. Most notably, he reinforced the principle that federal courts are obligated to exercise judicial review, by disregarding purported laws if they violate the Constitution. Thus, Marshall cemented the position of the American judiciary as an independent and influential branch of government. Furthermore, Marshall's court made several important decisions relating to federalism, affecting the balance of power between the federal government and the states during the early years of the republic. While some of his decisions were unpopular, Marshall nevertheless built up the third branch of the federal government, and augmented federal power in the name of the Constitution and the rule of law.