GDG- Underground Railroad Locations

[The Mills]

Hello All:

I was curious, how many underground railroad locations were there in Gettysburg and how many still remain?  I heard that the one at the Dobbin House is questionable at best.  Can anyone provide a list of locations that were locations on the historical railroad, ones that still exists today, and ones that are are questionable as possible locations?  I hope this isn't asking for too much.

Thanks
Andy