Explain what happened in Marbury v. Madison.

Marbury v Madison established the precedent of Judicial Review reviewing an act of Congress and judging whether or not it is constitutional. The court first invalidated an act of Congress in 1794 but it was the landmark case of Marbury v Madison in 1803 which set forth the rationale for the Supreme Court's assumption of this power, which is not granted to it by the Constitution.

The U.S. Supreme Court case Marbury v. Madison (1803) established the principle of judicial review—the power of the federal courts to declare legislative and executive acts unconstitutional. ... Marbury sued the new secretary of state, James Madison, in order to obtain his commission.