When the Civil War began in 1861, the North's more developed industrial capacity became essential to Union victory over the Confederacy, and Buckeye Furnace contributed to that strength through iron production. The Hanging Rock Iron Region of Ohio became a center of iron production because its iron was considered superior, and furnaces like Buckeye Furnace converted local iron ore, limestone, and charcoal into iron. During the war, demand for the region's iron grew so immense that many ironmasters loaded pig iron while it was still hot. Buckeye Furnace, one of 69 charcoal iron furnaces in the Hanging Rock Region, produced military hardware including cannons, large mortars, rifle barrels, and armor plates, while its iron also went into steam engines for railroads and ships, rails for railroads, and armor plates for the first ironclad Union vessel, the USS Monitor.