The U.S. Supreme Court currently consists of 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 court's 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 Court's 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 size of the court was first altered by the Midnight Judges Act of 1801 which would have reduced the size of the court to five members upon its next vacancy, but the Judiciary Act of 1802 promptly negated the 1801 act, restoring the court's size to six members before any such vacancy occurred. As the nation's boundaries grew across the continent and as Supreme Court justices in those days had to ride the circuit, an arduous process requiring long travel on horseback or carriage over harsh terrain that resulted in months-long extended stays away from home, Congress added justices to correspond with the growth: seven in 1807, nine in 1837, and ten in 1863. At the behest of Chief Justice Chase and in an attempt by the Republican Congress to limit the power of Democrat Andrew Johnson, Congress passed the Judicial Circuits Act of 1866, providing that the next three justices to retire would not be replaced, which would thin the bench to seven justices by attrition. Consequently, one seat was removed in 1866 and a second in 1867. Soon after Johnson left office, the new president Ulysses S. Grant, a Republican, signed into law the Judiciary Act of 1869. This returned the number of justices to nine (where it has since remained), and allowed Grant to immediately appoint two more judges. President Franklin D. Roosevelt attempted to expand the court in 1937. His proposal envisioned the appointment of one additional justice for each incumbent justice who reached the age of 70years 6months and refused retirement, up to a maximum bench of 15 justices. The proposal was ostensibly to ease the burden of the docket on elderly judges, but the actual purpose