The Hanging Rock blast furnaces varied little in design, resembling flat-topped pyramids built of sandstone block, with narrow tops rising 35-40 feet from broad bases and brick linings made from clay mined nearby. Chunks of iron ore and limestone, along with charcoal for fuel, were dropped into the open top, while tall wooden buildings on stilts surrounded the furnace to provide access and keep the charcoal dry. After the charcoal was ignited, air was forced through openings at the base, and the hot liquid was molded in beds of sand into blocks called “pigs.” These blast furnaces produced an average of 3000 tons of iron a year, and the pig iron was loaded onto railroad cars for shipment to foundries in Cincinnati and Cleveland, to the east coast, and even to Europe.