There are two well known aerial drawings (maps) of Pen Argyl dating to 1894 and 1917, but I just came across one online from 1885. It is especially interesting because it shows the Jackson Quarry being worked from the opposite direction. Also of note is the turntable below the Albion Quarry and the multitude of narrow gauge railroad tracks going to the shanties on the adjacent dump. This quarry had only been open for seven years when the drawing was made, but was already the largest in town.
http://www.flickr.com/photos/normanbleventhalmapcenter/2675120408/sizes/o/