Underwood Furnace was built three-quarters of a mile north in 1846-47 by James C. Sloo and Leonard White. It was a brick structure with a steam-powered air blast, using locally made charcoal fuel to produce pig iron from ore mined nearby. Iron was shipped by steamboat to fabricators. After 1848, operations were transferred to the neighboring Hopewell Furnace. Kentucky had been a major iron producer since 1791, ranking third in the U.S. in the 1830s and eleventh in 1965. Charcoal timber, native ore, and limestone supplied material for numerous furnaces making pig iron, utensils, and munitions in the Hanging Rock, Red River, Between Rivers, Rolling Fork, and Green River regions. The charcoal-furnace era ended in the 1880s with depletion of ore and timber and the use of modern methods.