May 21, 1953: On the mound: The origin of the pitcher's mound

This is the first strip in which there is an actual pitcher's mound, and not a flat spot of earth. Of course the later mound is a lot wider, but it's not actually much shorter.

One flaw with the premise of this strip: when the other team is up to pitch, wouldn't it help them just as much?

May 18, 1953: On the mound: The baseball changes hands

In an earlier strip the baseball was Schroeder's, and Charlie Brown told him to take it and run home when his team was in the lead.

I think this is the first use of the term "good grief."

April 6, 1953: On the mound: Charlie Brown dodges his first line drive

A notable series much later has Charlie Brown getting hit by a line drive and lamenting how his reflexes are going as he gets older.

April 2, 1953: On the mound: I think they're scoring a little high

How does a team earn 89 runs in a game that's not even over yet?

One potential problem, avoided I think, with this strip is the use of the word "home" in the last panel, which is a baseball term. Schulz plants the idea of Schroeder's home life in the reader's mind in the third panel however, which allows CB's line in the last to be more cleanly read as referring to Schroeder's house instead of home plate, would would have confused the joke.

March 31, 1953: On the mound: Schroeder the catcher

This is the very first of a staple strip-type of Peanuts throughout its history, Charlie Brown the pitcher interacts with a member of his team who has come up to talk to him during a lull in the game. It even has Charlie Brown's usual expression of annoyance at having to put up with one of his teammates. It is missing the pitcher's mound, but that's fairly minor.

This is also, to my memory, the first time Schroeder has been catcher, which pretty much becomes his set role on the team.