Columbia subject headings:
Building, Iron and steel.
Civil engineering--History--19th century.
Iron and steel bridges.
Iron, Structural.
Steel, Structural.
Harvard subject headings:
Building, Iron and steel.
Civil engineering--History--19th century.
Iron and steel bridges.
Iron, Structural.
Steel, Structural.
Princeton subject headings:
Building, Iron and steel--History--19th century.
Civil engineering--History--19th century.
Iron, Structural--History--19th century.
Steel, Structural--History--19th century.