The ratification of the United States Constitution…
February 1790 CE
Its powers are detailed in Article Three of the Constitution.
The Supreme Court is the only court specifically established by the Constitution while all other federal courts are created by Congress.
Congress is also responsible for conferring the title of "justice" to its members, who are known to scold lawyers for inaccurately referring to them as "judge", even though it is the term used in the Constitution.
The Court first convenes on February 2, 1790 with six judges where only five of its six initial positions are filled.
The sixth member, James Iredell, will not be confirmed until May 12, 1790.
Because the full Court has only six members, every decision that it makes by a majority will also be made by two-thirds (voting four to two).
However, Congress has always allowed less than the Court's full membership to make decisions, starting with a quorum of four justices in 1789.