From the website cited above:

The PA climbing guidebook is he first book to document statewide climbing history for a state that has little documented information until now. The book is over 500 pages, making it the largest statewide guidebook in print.

It's remarkable that Pa. has gone from obscurity to record-breaking elucidation climbwise by just one book. Who woulda thunk it?
(But doesn't this thread belong in the Books forum?)