Cast iron
Cast iron is made from pig iron, which is the product of smelting iron ore in a blast furnace. Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are then added to the melt before the final form is produced by casting.
James Bogardus
Bogardus attached plaques to his cast-ironwork that read: "James Bogardus Originator & Patentee of Iron Buildings Pat' May 7, 1850." After his invention of cast-iron in the early 1850s, he demonstrated the use of it in the construction of building facades, especially in New York City for the next two decades. He was based in New York, but also worked in Washington, DC, where three cast-iron structures erected by Bogardus in 1851 were the first such constructions in the capital. The success of the cast-iron exteriors from 1850-1880 led to the adoption of steel-frame construction for entire buildings.