The Charcoal Barn stored the furnace fuel, charcoal, which was made from hardwood trees cut from the surrounding forest. Charcoal was used because it provided much greater heat than wood, and temperatures of 3,000 degrees Fahrenheit were required to melt iron ore. A Connecting Shed joined the Furnace and the Charcoal Barn so workers could haul the fuel to the top of the stack. The storage barn had a gabled slate roof. In 1856, a fire started by a hot coal burned the Charcoal Barn to the ground, and after the fire the building was enlarged by a third. The reconstruction date of 1856 appears on the outside east wall above the keystone of the window archway. The sandstone building housed the fuel for the furnace operation, later deteriorated without a roof, and was reconstructed in 1987 after volunteers in 1987 to 1988 labored with period tools on the mortise and tenon joints and beams. Today the Charcoal Barn houses the Association's museum.