Marbury v. Madison is perhaps the most important Supreme Court of all time because it established the Court’s power of judicial review. The Constitution—which only establishes that there will be a judicial branch of the federal government—left it to Congress to decide how the federal court system would actually work. So the Federalist controlled Congresses under Washington and Adams passed laws—judiciary acts—setting up federal court system.
When Adams and the Federalists lost the presidency and control of Congress to Jefferson’s and the Democratic-Republicans in the election of 1800, the lame-duck Federalist Congress passed the Judiciary Act of 1800, creating new judgeships for Adams to appoint Federalists to so that they could maintain control of one of the branches of government.
Jefferson and his Secretary of State, future President James Madison, refused to deliver all of Adams’ last minute appointments, leading William Marbury—whom Adams had appointed as Justice of the Piece for the District of Columbia—to sue to have the Supreme Court force Madison to give him his appointment.
Instead of siding with Marbury, Marshall’s court found the Judiciary Acts to be in violation of the Constitution. The Court asserted that laws passed by Congress that violated the Constitution were null and void. They called this process of checking to see if a law was Constitutional or not judicial review and it quickly became the most import role of the Supreme Court, even though it is not in the Constitution itself.