When will Congress change the size of the Supreme Court?
In the past, Congress has changed the number of Justices on the Supreme Court from six to ten.
Currently, there are nine people on the Supreme Court.
What is stopping Congress from adding to or subtracting from it now?
Vacation.
It has been nine Justices since 1869.
It was:
Ten in 1863
Nine in 1837
Six in 1789.
The source is the U.S. Supreme Court website.