Missouri State Association.
A convention of base ball players was held at the Philharmonic Hall, St. Louis, April 22d, to form a State association. The delegates to the convention were...Athlete Club, Chas. D. Paul...
-New York Clipper, May 2, 1868
Charles Paul is mentioned in one other baseball-related source that I've seen and it happens to be one of the most significant sources that we have.
The above image comes from the September 3, 1859 issue of the New York Clipper and mentions an unnamed St. Louis baseball club that was organized on August 1, 1859. It is the earliest known reference to a St. Louis baseball club that we have. The text, which is difficult to make out in the picture, reads as follows:
Club Organized. - A base ball club was organized in St. Louis, Mo., on the 1st inst. It boasts of being the first organization of the kind in that city, but will not, surely, long stand alone. It numbers already 18 members, officers as follows: President, C.D. Paul...
Here's a better image of the squib, from the Mears Collection:
One of the big questions I have about the 1859 source is whether or not this unnamed club was playing the New York game of baseball. There is nothing in the source material that explicitly states that this is the case but I do assume that the unnamed club was playing the NY game. The fact that Paul was later involved with a club that was, without question, playing this game gives me some confidence that this assumption is true. It's not the best evidence but it is some sort of evidence. And given that we had no evidence at all, prior to this, I was excited when I found it. So we have that going for us.
I don't have a lot of information about Paul but I do know that he was born in Missouri in 1840 and that he was living in St. Louis in 1860, working as a printer. His older brother, Edmund Paul, was also a member of the unnamed club and, in 1860, the two were living with their father. And I guess, now, I also know that Charles Paul was a member of the Athletic Club in 1868.
And a quick note on the name of this 1868 club. The contemporary references in April and May of 1868 refer to them as the Athletes but Tobias refers to them as the Athletics and specifically mentions Edward McKeon, one of the club's delegates at the convention, as an officer of the Athletics. There are also contemporary references to the Athletic Club so I'm going to refer to them as the Athletics.