The Hoover-Mason Trestle was an elevated rail line built to transport raw materials to the blast furnaces and was in use from 1907 until 1995. Named after the engineering firm that designed and built it, the trestle carried electric-powered transfer cars that delivered iron ore and limestone from a storage area about a half-mile to the east, while recently produced coke arrived in hopper cars from the Coke Works near Hellertown, PA. Each car could carry about 150 tons of material, and the cars ran back and forth along the trestle 24 hours a day, 365 days a year, fueling the constant production of iron in the blast furnaces. The Philadelphia, Bethlehem, and New England Railroad carried molten iron from the blast furnaces to steelmaking furnaces and foundry operations and carried molten slag to a cooling area. Railroad cars and trucks also brought in materials from outside sources, moved materials throughout the plant, and shipped out products.