Historians tell us that the Industrial Age began with the invention of the steam engine in the 1840s. But really it began a century earlier with the founding of the iron industry in America. Iron became the basic material of industry, eventually helping to build the factories and equipment to make it run.

The only surviving intact charcoal cold blast furnace in the Western Hemisphere, the Cornwall Iron Furnace in Cornwall, Pennsylvania, was the heart of a vast industrial plantation for over 140 years. It and other iron furnaces dotted the Pennsylvania countryside in the 18th and 19th centuries. Around them grew villages, with artisans' shops, stores, schools, churches, and the home of a wealthy ironmaster. The areas around these furnaces supplied the iron ore, limestone, and wood for charcoal, .all of the raw materials necessary for the smelting process. At its peak, the Cornwall iron plantation consisted of about 10,000 acres.

The Early Years
In the 1730s, Peter Grubb, a stone mason, began mining nearby. In 1742, he established the furnace, naming it Cornwall after his father's birthplace in England, which remained in operation until 1883. Although the British Parliament attempted in 1750 to restrict production of iron in the Colonies, the output continued to rise. Pennsylvania was the leading producer, smelting one-seventh of the world's iron.

By the 1850s, small villages, housing miners and workers, grew up around the furnace. The buildings were simple structures of stone and brick.

When Peter died in 1751, the property passed to his sons, Curttis and Peter. By 1798, the Grubb family said out to Robert E Coleman. He was so successful that he became one of Pennsylvania's first millionaires.

The Role of Iron in Everyday Colonial Life
Blacksmiths have long fashioned wrought-iron products. At the time of American settlement, most tools and many household items in Europe were made at least partially of iron. Emigrants to Colonial America sacrificed many comforts but were unwilling to do without iron. Since Native Americans produced no iron and importing iron and iron products from Europe was prohibitively expensive, early settlers had a powerful incentive to master ironmaking.

Though the techniques of ironmaking have been refined over many centuries, the process has remained essentially unchanged. Ironmakers used intense heat to separate the iron in iron ore from impurities, the waste is discarded, and useful products are fabricated with the remaining iron. Overall, ironmaking is an arduous process. Feeding a blast furnace is like feeding a noisy, fire-breathing dragon, surrounded by flames, smoke, ashes, sparks, and soot, and whose main product by volume is carbon monoxide. Ironmaking requires enormous amounts of fuel to bum hot enough to melt the iron ore, or at least soften it enough so the iron can be isolated by repeated hammering. Limestone is the flux. And finally, there needs to be a way to apply large amounts of oxygen needed for the furnace fire to burn hot enough. The entire smelting process required a large number of skilled and unskilled workers.

The Ironmaking Process
The first step in smelting iron is to remove oxygen from the iron by direct induction. This took place in a bloomery, so named for the bloom, the mass of iron as it lay in the coals.

Cornwall smelted its iron ore with a blast furnace and indirect reduction in high heat. While it’s not necessary to melt the rocks to make wrought iron in a bloomery, it is necessary to melt the rocks to make cast iron in a blast furnace. This was a flat-topped, truncated, hollow pyramid, usually 25 to 35 feet high and constructed in three layers—a stonework stack, a sandstone or firebrick lining, and a layer of rubble and other materials between the stack and the lining that provided insulation and allowed for expansion and contraction.

Iron workers fed, or charged, the blast furnace at regular intervals with charcoal, iron ore, and limestone placed into its mouth. Charging by buggy or basket continued day and night for as long as the furnace was in blast. The massive stonework of the furnace structure provided containment for an inferno of burning charcoal and functioned as support for the hollow, bottle-shaped lining of the furnace, where the iron was actually separated from the ore.

The shape of the furnace lining was critical to its operation. Downward from the mouth, the lining widened to about nine feet until it reached its center, the bosh, where the rocks would melt. A funnel formed below the bosh, where the lining wall sloped inward to about four feet. This shape provided necessary support for the burning mixture so that the blast could pass through unhampered. Hot, molten rock material trickled down and funneled into the crucible which contained it, with heavy iron on the bottom and impurities forming a layer on top. Workers emptied the crucible twice a day, yielding about two tons of cast iron at each tap.

Creating Oxygen
To maintain intense furnace temperatures hot enough to melt rocks, it was imperative to establish a steady stream of compressed air, or blast. As the blast bubbled up through the burning mass in the furnace, it fed oxygen to the fire, hastening the separation of the iron from the ore.

The first universal blast equipment was a water-powered bellows that compressed the air and then fed it to the furnace through a pipe called a tuyere. Soon pairs of closed blowing cylinders or blowing tubs, still powered by water wheels, began to replace the old leather bellows. The water wheel drove pistons up and down reciprocally in the tubs, which had been lined with leather to make them airtight. By a simple system of intake and exhaust valves, air from the tubs was forced into a central mixing box and then through a duct to the tuyere.

Blast operations became even more efficient in the 19th century as water turbines and steam engines replaced the water wheels, which enabled many furnaces to increase the number of tuyeres. In 1841, the ironmaster installed a steam engine at Cornwall.

Furnace Operations
It took two days to blow in, or start, a new furnace or to restart a furnace that had blown out for repair or annual cleaning, a necessary procedure that took six weeks to two months. Fillers loaded charcoal into the tunnel head, or mouth of the furnace, until the furnace was completely full. The charcoal was set on fire at the top and allowed to burn all the way to the bottom. The fillers then fed the furnace with charcoal until it was full again, this time burning from the bottom until the stack was hot and nothing but glowing coals remained.

Then it was time to charge the furnace, adding alternate layers of charcoal, iron ore, and limestone to the fiery mass at regular intervals. Fillers charged the furnace day and night with the proportions of these three materials as deter-mined by the founder based on his basic analysis of the ore on hand. Charging continued day and night for as long as the furnace was in blast, 18 to 20 charges a day. As the temperature approached 2500 to 3200 degrees F in the bosh, the rocks began to melt and the furnace to work. Workers removed the slag and discarded it every hour or half hour. In this continuous process, it took about 40 hours for a batch of iron ore to go from mouth to hearth.

Twice a day, workers tapped the furnace. At about noon and midnight, at the founder's signal, workers gathered in the casting house at the bottom of the furnace stack. The keeper unplugged the cinder notch, the top hole in the dam stone or door, which allowed the remaining liquid slag to drain off to one side. After the slag cooled, workers broke it up and discarded it. They then removed the lower plug in the dam stone and red hot, molten iron flowed through channels into the molds already prepared by the molders in the sand floor of the cast house.

Guttermen guided the flow from the large channel into the smaller molds formed at right angles. This figure resembled a sow with nursing piglets, so the main product of the blast furnace became known as pig iron. Pigs, the first step in extracting iron from ore, had a flat side and could be stored or transported to market or to the forge for further refining.

Workers in the casting house also cast some of the liquid iron as ironware by molders, who ladled molten iron from the furnace into special casting flasks to produce common items such as skillets, kettles, and stove plates. Using skillfully carved molds, molders often cast stove plates with intricate designs that included the furnace and ironmaster's name, date of casting, Bible verses, and other mottoes and symbols.

The Cornwall iron furnace remained in operation until 1883, when newer furnace operations fueled by anthracite coal made it obsolete. The abandoned furnace remained untouched until Margaret Coleman Freeman Buckingham, the great-granddaughter of Robert Coleman,. donated it to the state in 1932.

Cornwall Iron Furnace Today
The furnace site today includes remnants of the original 18th-century industry—the19th-century furnace building and connecting shed, wagon shop, and blacksmith shop, abattoir, and charcoal barn, as well as stone coal bins and roasting oven. The former manager’s house and office and stable are now occupied privately. The flooded open-pit iron mine lies just up the road from the furnace and the former ironmaster’s house is now the centerpiece of a retirement community across the road.