Catoctin Furnace grew in the 1700’s as a busy industrial village around an iron-making complex begun by James Johnson with financial assistance from Thomas Johnson, a governor of Maryland during the Revolutionary War, and later owned by attorney Baker Johnson. The site was chosen for nearby natural resources and because transportation was poor, with no canals, trains, or trucks to move raw materials that weighed at least 10 times more and took up 100 times more space than the finished product. The Mountain Tract, much of it now Cunningham Falls State Park and Catoctin Mountain Park, supplied hardwoods for charcoal, iron ore, limestone, and water power. Isabella, built in 1858, was the second of three furnace stacks; the first, built in 1776 and probably located behind Isabella, likely used water power from Little Hunting Creek to run its bellows, while Isabella and the third stack, Deborah, used steam-driven pistons to create the air blast that fanned the fire. The three furnaces had different capacities, and Isabella produced up to 3300 tons of pig iron annually. Iron making began by charging the furnace from the top with charcoal, iron ore, and limestone, which acted as a flux and mixed with impurities to create slag, then heating it to 3000 degrees F to melt the ore. The furnace ran 24 hours a day during production, and about every 12 hours foundry workers tapped it so molten iron could flow into channels on the casting shed floor, where it hardened into iron pigs or was cast in wooden molds. Pig iron took its name from a shape that reminded foundry men of a sow suckling a litter of pigs. Iron from the furnace became cannon shells, stoves, tools, nails, and wheels. A 200 foot rock retaining wall once supported wooden buildings and sheds that housed raw materials, and the wall and furnace stack were built of local fieldstone cut by hand, while the casting shed with its wood-shingle roof was reconstructed in 1975 and the other stone remains are original.