Columbia subject headings:
Harvard subject headings:
Bridges--United States--Design and construction--History.
Ellet, Charles, 1810-1862.
Roebling, John Augustus, 1806-1869
Suspension bridges--Design and construction--History.
Princeton subject headings:
Ellet, Charles, 1810-1862.
Engineers--United States--Biography.
Roebling, John Augustus, 1806-1869.