ScientificAmerican1920-09-11.jpg Scientific American 1920-09-04ThumbnailsScientific American 1920-09-18Scientific American 1920-09-04ThumbnailsScientific American 1920-09-18Scientific American 1920-09-04ThumbnailsScientific American 1920-09-18Scientific American 1920-09-04ThumbnailsScientific American 1920-09-18

New York's sky-line artisans: structural iron workers.