With the help of old aerials and an old plat atlas of Allentown that shows the land they bought I've mapped the portion east of Kutztown: http://www.openstreetmap.org/?relation=1400060
you can easily switch to topos and aerials to see what still exists (for example, crossing Grange Road north of Hamilton Boulevard).
West of Kutztown, http://www.historicmapworks.com/Map/US/ ... nsylvania/
(as well as individual town maps in that atlas) shows the general alignment (and that of the South Mountain and Boston Railroad, another unfinished line). A quick check of topos shows a definite grade north and east of Hamburg (along the city limits) and a tunnel here: http://mapper.acme.com/?ll=40.54942,-75.93935&z=16&t=T
as well as at least portions of grading all the way to Kutztown.
Here's the grade approaching the tunnel portal: http://maps.google.com/maps?ll=40.55194 ... 25,,0,2.52
and a whole bunch of tractors on the other side of the road