In the late 1880s, an abrupt change of steel replacing wood and stone in structural materials brought about a demand for a new type of worker – ironworkers. Ironworkers work on the construction of industrial, commercial, and large residential buildings, as well as on towers, bridges, stadiums and prefabricated metal buildings. They erect and install pre-cast beams, columns and panels in accordance with engineered drawings.
Union: International Association of Bridge, Structural, Ornamental and Reinforcing Iron Workers http://www.ironworkers.org/