Charcoal iron production in Ohio was centered in the Hanging Rock Region, which extended from Hocking County to the Ohio River and included portions of northern Kentucky. The region encompassed 1,800 square miles rich in iron ore and limestone and covered by forests that supplied raw material for charcoal. Union Furnace, built in 1826, was the first furnace in the region. By 1856, sixty-five furnaces operated there, and the Ohio furnaces alone produced 105,500 tons of pig iron that year. Demand for iron from the Hanging Rock charcoal furnaces increased during the Civil War because of the need for munitions, but after the war the furnaces declined, and by the beginning of the twentieth century the once prosperous industry had all but disappeared. The decline resulted from changes across the American iron industry in the second half of the nineteenth century, including the introduction of cheaper coke fuel, the construction of much larger furnaces in other iron-making areas, the economic shipment of Lake Superior iron ore to Pittsburgh and other producing centers after the war, and the rise of integrated corporations that small charcoal furnaces could not compete against. When Jefferson Furnace of Oak Hill closed on December 29, 1916, the last of Ohio's charcoal furnaces ceased operation, and decaying furnaces, scrapped equipment, and disbanded communities left stone furnace stacks as reminders of the once thriving industry.