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The ironmaking industry had an important role in America's technological and industrial development. It was one of the country's earliest industries. There are many remnants of iron furnaces scattered around the country; most are just languishing stonework, but a few have been preserved as examples of a fascinating industry. 


Cornwall Iron Furnace, near Harrisburg, Pennsylvania, sign showing the iron making process
The mechanics of the furnace: iron ore into pig iron. 

In past issues two of the most interesting of the remaining charcoal iron furnaces in the country were discussed: Hopewell Furnace in Pennsylvania and the Tannehill Ironworks in Alabama.  Ironworks were an integral part of the foundation that allowed for America's industrial revolution. A third Ironworks, Cornwall Iron Furnace, located about 30 miles east of Harrisburg, Pennsylvania, is the only surviving intact charcoal cold-blast iron furnace in the Western Hemisphere.  Cold-blast technology (the air was not preheated before being blown into the furnace) was prevalent until the 1840s, when the hot-blast iron furnace became necessary to burn anthracite coal.  





Blast furnace at Cornwall Iron Furnace, near Harrisburg, Pennsylvania,

The blast furnace building where iron ore, limestone, and charcoal became pig iron. Originally separate buildings were clustered around the furnace stack. In the mid-nineteenth century the furnace was remodeled into this larger building with its elegant fašade and Gothic Revival detail. 

Cornwall Iron Furnace is probably the best single locations in the country to view an iron furnace in terms of the operational aspects of the cold-blast iron making process. It still has, not only the intact furnace, but the entire furnace house, supporting buildings, and ironmaster's and laborers' residences. One gets a true feeling for what the community must have looked like. This was a charcoal iron furnace plantation, a self-sustaining community. The historical site is five acres in size. The actual plantation was closer to 10,000 acres, with its own agricultural fields and pastures and woodlands needed to produce charcoal. Perhaps 5,000 - 6,000 of those acres would be necessary to produce charcoal on a sustained basis (charcoal production at a nearby iron plantation was discussed in the Fall 2011 issue. See article )    

Stone buttresses at Cornwall Iron Furnace, near Harrisburg, Pennsylvania
Stone buttresses built to support the railway that transported ore from the mine to the site.

The furnace operated from 1742 to 1883 and, like other furnaces of its time, was located near four key requirements for iron production: iron ore, woodlands for charcoal production, limestone (a flux or chemical agent that cause the slag to accumulate impurities), and water power. Peter Grubb began mining in the area in the 1732 and established the furnace in 1742, naming it after his birthplace in England. The British Parliament discouraged iron production in the colonies, but iron output grew and by the time of the American Revolution the iron industry in the colonies exceeded that of Great Britain.  With 80 furnaces in nine of the colonies, America accounted for about one-seventh of the world's iron output. Pennsylvania, with about 20 furnaces, had the largest number of any colony. The American Revolution likely would not have been successful without the locally-produced ordnance and ammunition.

Near Cornwall, visible from the road, are the Cornwall Ore Banks.  This deposit of magnificently rich magnetite ore remained one of the most valuable iron ore bodies in the country until the discovery of the Lake Superior deposits. This is what caused Peter Grubb to invest in an iron furnace. When the mine was worked, it was the largest open-pit iron mine in the eastern United States.  After the furnace closed Bethlehem Steel Company purchased the pit mine and operated it until 1973 when flooding caused by Hurricane Agnes closed it. Today it looks more like a charming lake surrounded by rock cliffs. The pit is about 500 feet deep.    

Window in abattoir at Cornwall Iron Furnace, near Harrisburg, Pennsylvania

The buildings have many interesting artistic features,
like this window on the abattoir.

The normal beginning point of the furnace tour is the visitor's center, located in what was the charcoal barn.  This barn has four large rooms or bays that were used to store the charcoal, produced in the surrounding forests by colliers and transported there by teamsters. The barn was filled using ground level doors. The barn held enough charcoal for 100 days of production and, when the supply grew beyond the ground openings, roof ladders were used to add charcoal via roof doors. All the other bays opened to the second bay that has access to the furnace by the connecting shed. The visitor's center contains sets of exhibits centered on the furnace history, charcoal production, iron ore mining, and the ironmaking process. Some of the products produced at the furnace are on display. The furnace tour stars with an orientation video in the first charcoal bay before entering the furnace building via the connecting shed.   
Old cart used at Cornwall Iron Furnace, near Harrisburg, Pennsylvania
Much of the equipment is still at the furnace,
like the carts used to haul iron ore and charcoa

The furnace building is only accessible by a guided tour that starts on the charging floor.  The furnace building is actually several connected buildings assembled around the furnace stack. The building was remodeled in the mid-nineteenth century in the Gothic Revival style. The charging floor is where fillers, under direction of the founder, dumped buggy loads of iron ore, limestone, and charcoal into the mouth of the furnace. The visitor gains a good overview of the 32 foot furnace from the charging room, including its general shape and construction. Various equipment was used to feed the furnace is still there, including the buggies.  The larger ones were for charcoal and the smaller ones for the heavier iron ore.     

Cannon produced at Cornwall Iron Furnace, near Harrisburg, Pennsylvania
One of the products of the furnace was cannons.

The tour moves on to the Wheel Room, containing the blast equipment. This is suspected to be the sole remaining example of this type of equipment that is still intact. The room is dominated by the "Great Wheel," 24-feet in diameter and weights four tons. It powers the wood and leather bellows that pumped air into the furnace to create greater heat. The wheel is actually turns during the tour.  Next comes the Engine Room, containing a working steam engine that powered the blast equipment.  It was installed about 1841 and is still capable of powering the wheel.   

At the bottom of the furnace is the Casting Room (also called the cast house or casting floor). This is where the molten iron flowed out of the furnace and was molded into pig iron or cast iron products, such as stove plates, pans,  and cannon balls. This is the opposite view of the furnace as from the charging room and the visitor get a feeling for the massive structure of the furnace. There is one of 42 cannons cast for Revolutionary War naval frigates on display.     

casting house at Cornwall Iron Furnace, near Harrisburg, Pennsylvania
The casting house at the bottom of the furnace stack where the iron was discharged. Notice the pig iron in the foreground
Near the building is a roasting oven used to roast the iron ore to remove sulphur, which would cause problems in the smelting process. Layers of charcoal and iron ore were loosely packed to allow for upward movement of the air. Also nearby are large stone coal bins used to store coal that heated the workers houses and the ironmaster's mansion.  Other stone buildings are the blacksmith shop, wagon shop, and abattoir (smokehouse and butcher shop). There are other related sites, not owned by the historic site,  that were part of the original iron plantation. While they cannot be visited, they are easily observed and are near the furnace. These include a stable, the manager's house and mine office, the open pit mine (now flooded), the miners village, an office building, and the ironmaster's mansion. You will probably drive through the miners village when you enter town. The buildings are stone; all constructed alike, and form a quaint picturesque "company town" image.   




Profitability of the furnace decreased after the Civil War when new steel mills opened in cities like Pittsburg and Bethlehem. After losing money for a decade the furnace closed in 1883. The furnace property was donated to the Commonwealth of Pennsylvania in 1932 and is operated today as a state historical site. It is a national historic mechanical engineering landmark. The report on the landmark notes "that Cornwall was spared the depredations of weather and salvage is nothing less than a miracle of industrial archeology" and that it survives "as the only 18th/19th-century American blast furnace with its original fabric."    

Author and Photographer: Tom Straka is a forestry professor at Clemson University in South Carolina and has a keen interest in roadside history. Doug Page is a retired Bureau of Land Management forester and resides in Cedar City, Utah.

For more information:

Cornwall Iron Furnace:


ExplorePAhistory.com-Cornwall Furnace Historical Marker:


Cornwall Iron Furnace – National Historic Mechanical Engineering Landmark:


Cornwall Iron Furnace – Pennsylvania Trail of History Guide by Susan Dieffenbach:


A Blast from the Past: Cornwall Iron Furnace by Sharon Hernes Silverman: http://www.portal.state.pa.us/portal/server.pt/community/trails_of_history/4287/cornwall_iron_furnace_(ph)/472318







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