Henry:
You may want to look at this file I created some years back. It traces PCL history from its inception in 1903 up through the 2004 season. For each year it includes the following information: a listing of the teams, Major League affiliations, the schedule length, playoff format used, changes to the league structure (i.e. teams folding, realignment, etc.), along with related notes where appropriate.
In short, pretty much all the league-level details one may be interested in.
It is in .rtf format (I put it together in Wordpad) and is contained in the attached .zip file.