Article 3 of the U.S. Constitution (1788) states that the “judicial Power of the United States, shall be vested in one supreme Court.” It goes on to describe the high court’s jurisdiction, but it does not specify how the court was to be formed or how many justices it would consist of. These matters were left to Congress, which in 1788 (the year the Constitution was ratified) passed the first Judiciary Act, formulating the court’s original organization; it had just six members: the chief justice, plus five associates. Subsequent congressional acts have modified the Supreme Court’s organization and jurisdiction.

Since 1869 the Court has consisted of nine members: the chief justice and eight associates who, once named, serve for life. Justices are appointed by the president but must be approved by the Senate (according to Article 2 of the Constitution). To avoid partisanship, Congress is prevented from lowering the salaries of any of the justices, and justices can only be removed from the bench by impeachment (a formal document that charges a public official with misconduct). Cases reach the high court through appeal (lower-court decisions that are formally challenged), and the justices make their rulings based on a majority vote.