The total strength of the Supreme Court of the United States is nine members: one chief justice and eight associate justices. The U.S. Constitution does not specify the size of the Supreme Court, nor does it specify any specific positions for the courts members. However, the Constitution assumes the existence of the office of the chief justice, because it mentions in Article I, Section 3, Clause 6 that "the Chief Justice" must preside over impeachment trials of the President of the United States. The power to define the Supreme Courts size and membership has been assumed to belong to Congress, which initially established a six-member Supreme Court composed of a chief justice and five associate justices through the Judiciary Act of 1789. The number of Justices on the Supreme Court changed six times before settling at the present total of nine in 1869.