The Judiciary Act of 1789 was signed into law, establishing the U.S. federal judiciary and setting the number of Supreme Court Justices at six.

The Judiciary Act of 1789 is a United States federal statute enacted on September 24, 1789, during the first session of the First United States Congress. It established the federal judiciary of the United States. Article III, Section 1 of the Constitution prescribed that the "judicial power of the United States, shall be vested in one Supreme Court, and such inferior Courts" as Congress saw fit to establish. It made no provision for the composition or procedures of any of the courts, leaving this to Congress to decide.

The federal judiciary of the United States is one of the three branches of the federal government of the United States organized under the United States Constitution and laws of the federal government. The U.S. federal judiciary does not include any state court, which are completely independent from the federal government. The U.S. federal judiciary consists primarily of the U.S. Supreme Court, the U.S. Courts of Appeals, and the U.S. District Courts. It also includes a variety of other lesser federal tribunals.

The Supreme Court of the United States is the highest-ranking judicial body in the United States. Its membership, as set by the Judiciary Act of 1869, consists of the chief justice of the United States and eight associate justices, any six of whom constitute a quorum. Article II, Section 2, Clause 2 of the Constitution grants plenary power to the president of the United States to nominate, and with the advice and consent of the United States Senate, appoint justices to the Supreme Court; justices have life tenure.