I was going to suggest the Allegheny River CG by your description, that is about equidistant from your mentioned targets, but if you think you are going to set the coach in one place for a month and do the sightseeing you described, you had better look at your plan more carefully.
Pennsylvania is just packed with beautiful campgrounds. But to traverse the distances you have outlined night be a bit of the trug. Across Pennsylvania, most of the fast roads go east-west. If you are going across I-80, the last exit is like 310 and they are in miles....
Matt