[jjotto]

There is an official number, by the Circuit Judges Act of 1869.

[pa_dweller]

Ah, so I see:

Wikipedia - The Judiciary Act of 1869, sometimes called the Circuit Judges Act of 1869, a United States statute, provided that the Supreme Court of the United States would consist of the Chief Justice of the United States and eight associate justices, established separate judgeships for the U.S. circuit courts, and for the first time included a provision allowing federal judges to retire without losing their salary.[1] This is the most recent legislation altering the size of the Supreme Court.

Thanks.