Columbia subject headings:
Armored vessels--United States.
Monitor (Ironclad)
Harvard subject headings:
Iron industry and trade--United States--History--19th century.
Monitor (Ironclad)
Shipbuilding--United States--History--19th century.
Princeton subject headings:
Iron industry and trade--United States--History--19th century.
Monitor (Ironclad)
Shipbuilding--United States--History--19th century.