Why Are There 9 Supreme Court Justices?

Live Science reports:

Congress increased the number to seven in 1807, to nine in 1837, then to 10 in 1863.

Then, in order to prevent President Andrew Johnson, who was soon to be impeached, from naming any new Supreme Court justices, Congress passed the Judicial Circuits Act of 1866. This Act reduced the number from 10 to seven. The decrease was to take effect as the seats became vacant.

However, only two seats were freed up by 1869, so there were eight justices. Congress added one seat back in, and decided that there should be nine justices. The Judiciary Act of 1869 officially set the number, and it has not budged since.

Just a reminder.