Columbia subject headings:
Engineering--Pennsylvania--Huntingdon County--History.
Industrial archaeology--Pennsylvania--Huntingdon County.
Harvard subject headings:
Engineering--Pennsylvania--Huntingdon County--History.
Huntingdon County (Pa.)--Description and travel.
Industrial archaeology--Pennsylvania--Huntingdon County.
Princeton subject headings:
Engineering--Pennsylvania--Huntingdon County--History.
Industrial archaeology--Pennsylvania--Huntingdon County.