Columbia subject headings:
America's Industrial Heritage Project.
Historic sites--Pennsylvania.
Industrial sites--Conservation and restoration--Pennsylvania.
Pennsylvania--History.
Harvard subject headings:
America's Industrial Heritage Project.
Historic sites--Conservation and restoration--Pennsylvania.
Industrial sites--Pennsylvania--Conservation and restoration.
Industries--Pennsylvania--History.
Pennsylvania--History.
Princeton subject headings:
America's Industrial Heritage Project.
Historic sites--Pennsylvania.
Industrial sites--Pennsylvania--Conservation and restoration.
Pennsylvania--History.