The Judiciary Act of 1789 was a landmark piece of legislation in the early years of the United States, establishing the federal judicial system and providing for the organization and jurisdiction of the courts. Signed into law by President George Washington on September 24, 1789, the act created a comprehensive system of federal courts, including the Supreme Court, circuit courts, and district courts. It also established the principle of judicial review, which gives the Supreme Court the power to interpret the Constitution and determine the constitutionality of laws passed by Congress.

The act provided for a Chief Justice and five Associate Justices on the Supreme Court, who were appointed by the President and confirmed by the Senate. The court was given original jurisdiction over cases involving foreign diplomats, disputes between states, and certain types of federal crimes. Appellate jurisdiction was also granted to the Supreme Court, allowing it to hear appeals from lower federal courts. Additionally, the act established the office of Attorney General, who served as the chief law enforcement officer of the federal government.

The Judiciary Act of 1789 had significant impact on the development of the American legal system. It not only established the structure of the federal courts but also set forth the principles that would guide their decisions. The act's grant of judicial review to the Supreme Court has been interpreted over time to give the court broad powers to strike down laws and government actions that are deemed unconstitutional. This has made the Supreme Court a powerful check on the other branches of government and a protector of individual rights. As such, the Judiciary Act of 1789 remains an important milestone in the history of American law.