I found an interesting document. Over on pennywit, there is a discussion of the Judiciary. I recall from "civics class" that there always weren't nine justices and so I thought I'd take a look and found these sites.

The most information

Easiest to read and a PDF (.pdf)

"Before settling at nine in 1869, the number of Supreme Court Justices changed six times."

And the "Jesus factor?"

Religious affiliations, chronological

Summary of affiliations

Is it possible to serve in any office and be atheist?