Allison-Antrim Museum 

                                     Greencastle, PA

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Heavy Metal

Iron ore + limestone + charcoal + water power + labor = iron.  Because the Cumberland Valley was rich in all of the natural resources – iron ore, limestone, forests, and running water – needed to produce iron, it was the ideal place for the establishment of numerous iron works in the 18th and 19th centuries.  The eastern and western borders of Franklin County held the richest iron ore deposits in the Commonwealth of Pennsylvania, and perhaps in the nation, generating at least ten different ironworks in the county.  An ironworks complex, such as the Mont Alto ironworks, might have included the iron master’s mansion, cottages for the employees, gardens and working farms, livestock including horses and mules, one or two iron furnaces, charcoal pits, chafery (finery) forges, foundry, a rolling mill, and later a nail factory.  The ironworks were the largest single employers in their time period. At the Mont Alto Furnace alone, 500 workmen were employed. In 1840, Franklin County had eight operating furnaces, 11 forges, chaferies, and rolling mills. 

Ancient sites of iron ore bloomeries have been discovered in Rome, China, and Africa, dating from 200-600 BC. Archaeological evidence also indicates that there were bloomeries (simple iron furnaces) in the Jamestown Settlement area, which was founded in 1607. One of the main goals of the English, Spanish, and French explorers was to discover what natural resources existed in the New World and lay claim to that land for their country.  By the time of the American Revolution, products that were made of cast and wrought iron were in great demand. The economy, which was agriculturally driven, required a lot of cast and wrought iron products for tools, implements, nails, weapons, etc. To protect their own interests at home in England, the English manufacturers and producers of goods lobbied Parliament to enact laws (including the Iron Act of 1750) that prohibited products from being produced from raw materials in the colonies. Therefore, everything that was used on a daily basis by the colonists was supposed to be “Made in England,” not in the colonies. By the time the Iron Act of 1750 was passed, the colonies were producing one seventh of the world’s pig iron, wrought and cast iron products.  Perhaps, this was partially due because access to English iron products was much more limited inland than it was in the towns and cities along the coast, where waterways provided easier shipments of goods from England. English agents, who were supposed to be monitoring such industrial activities, were known to look the other way in exchange for a nice monetary bribe.  Although there were no furnaces and foundries in Franklin County before the Revolutionary War, there were furnaces in Cumberland County, Pennsylvania and Frederick County, Maryland. 

Baranabus Hughes, an Ulster Scot (a.k.a. Scotch-Irish) from County Donegal, was granted over 20,000 acres of land from Lord Baltimore in the mid-eighteenth century.  The land was mostly in Frederick County, Maryland but extended northward to the Mont Alto area in Franklin County, Pennsylvania.  Barnabus was one of the first settlers to mine the ore and establish three iron furnaces prior to the Revolutionary War at Mt. Aetna along the Beaver Creek, south of Cavetown; Rock Forge, which was located just south of the Mason-Dixon Line along the Leitersburg Road; and a third site southeast of Leitersburg, Maryland on the Antietam Creek.  Daniel and Samuel Hughes, sons of Barnabus, were well-known ironmasters during the Revolutionary War, and manufactured the first Maryland cannon and small arms at Rock Forge for the Colonial army.

The Mont Alto Furnace was built by Daniel and Samuel Hughes in 1807-1808 on land which is currently owned by Penn State Mont Alto.  Within a mile of the furnace, there were eight mines (eventually 17) from which the ore was dug.  Because there was insufficient water power, dams were built at two places on the Antietam Creek to provide power for the blast furnace and forges. In 1809 and 1810, two forges were built about four miles in distance from the furnace.  The forges were deserted in 1866. The foundry was built in 1815, and the rolling mill in 1832, with the nail factory being the last of the industries built in 1835.   It was only 15 years later that the nail factory burned and the abandonment of the rolling mill followed in 1867.

During the peak operation of the Mont Alto Ironworks, it took an acre or more of trees to supply the charcoal needed for one day's operation of the furnace. The furnace usually made three runs of molten iron per day. The cost per ton of iron was $20 - $21 per ton.

The Mont Alto cold-blast furnace was built against the side of a hill, as most furnace stacks were, so that the ore, limestone, and charcoal could be more easily loaded into the top of the 34’ stack.  The loading process was called charging the furnace.

The ironworks complex described above also included the iron master’s mansion, with a village of cottages not too far down the mountain in which the ironworkers lived.  The ironworks complex was a community unto itself with gardens and a company store, in which only the ironworks’ currency could be used. Shelter was provided for the horses and mules, pigs, chickens, and occasionally cows. During the winter months, a tutor was sometimes hired to teach the workers’ children.  Ironworks complexes were the plantations of the North.

William, Benjamin, and George Chambers (sons of Benjamin Chambers Sr., founder of Chambersburg, Pennsylvania) built Franklin County’s first iron furnace in 1783 at Mount Pleasant.  This furnace was closed in 1834 and the forge, which was nearby, closed in 1843.  In 1865, a second furnace, called Richmond Furnace, was built on the original site.

Other well-known furnaces in Franklin County included Caledonia, that was owned and operated by Thaddeus Stevens and James D. Paxton; Falling Spring; Franklin; Southern Pennsylvania Iron and Railroad Co. (Mount Pleasant); and Roxbury.  Foundries not owned by county iron masters included the Crowell Foundry in Greencastle, which was later owned and operated by the Geiser Manufacturing Company.  (See the notebook on J. B. Crowell and his foundry, which is located just inside the dining room door from the hallway.)

The colonies’ ironworks were essential to the success of the Colonial army during the Revolutionary War. The 18th and 19th century iron furnaces, foundries, rolling mills, blacksmith shops, and nail factories of the Cumberland Valley formed the foundation of the industrial revolution in Pennsylvania and other states, that changed our nation and the world in the late 19th century.

Take a look around the museum house, which was built in 1860, and notice how many things made of iron were used in its construction.

Did you find all of the following?  Iron was used for the lock boxes on the doors, doorknob and keyhole escutcheons, keys, radiators (great conductor of and provided radiant heat), 1860s air-conditioning grills in the outer walls, window hardware, door hinges, library and attic door latches, and shutter dogs 

The Process

The chemical processes which occur during the smelting of iron ore are very complex, some stages of which are mysteries even today. Very simply put, the carbon – C – from the charcoal and the oxygen – O – from the bellows created CO2 – carbon dioxide. As more oxygen is added, it interacts with the carbon to produce CO – carbon monoxide.  The elements of 3CO and Fe2O3 (iron oxide) interact with each other to produce on the other side of the equation – 2Fe (pure iron) + 3CO2, which is given off as gas.

Charcoal, which is made from slowly charring wood, provided the carbon for most of the early furnaces in this region.  Later, coke, another form of carbon, became the more efficient carbon-source-of-choice. Over an acre of trees a day was needed to provide enough charcoal to fire the furnaces three times each day.  Good hardwood trees, such as chestnut, hickory, ash, and oak, were used to make the charcoal. The trees that forest the mountain areas of today’s Franklin County are second and third growths because of the extensive cutting for the needs of the iron furnaces in the late 18th and 19th centuries. The trees were cut in four-foot lengths.  The logs were then stacked on end and formed into an igloo shape that was 15-20 feet in diameter at the base and eight feet in height, with small air holes around the sides and a narrow flue in the center.  Wet leaves and dirt were used to cover the structure and then the fire was lit.  The collier had to stay with it constantly to make sure the pile of wood did not burst into flames and burn into ashes.  After about a week, the collier would remove the dirt and leaf covering and rake the charcoal into a pile.  This was a dangerous job as the charcoal, if hot enough, could possibly burst into flames when exposed to air.

In this regional area, iron ore was mostly mined from surface mines.  Pieces of iron ore can still be found lying on the ground in the areas where furnaces once existed.  The fillers, the men who filled the furnace, were quite skilled.  Each mine produced a different quality of iron ore.  The fillers knew how to pick and choose amounts of ores from different mines to make the right combination to produce high-quality pig iron, for which the Mont Alto furnace was known.  Limestone and charcoal were also alternately added with the ore to the furnace stack in correct proportions for the smelting process. 

Blasts of cold air, produced by giant bellows, were interjected into the stack through openings called twyeres (pronounced tw-ear).  Running water, one of the natural resources required for the production of iron, was often harnessed behind dams, which produced the water power to operate giant water wheels, which powered the bellows.  The amount of oxygen added to the furnace was also perfected to a science.  The temperature inside the furnaces reached 2,600 – 3,000 degrees Fahrenheit, which is necessary to melt the iron ore.  

Flux is a substance used to promote fusion, especially of metals or minerals.  The limestone was used to help separate the impurities from the iron ore which then ran off as slag.  Limestone, which is very plentiful in Franklin County, was dug from the open fields and hauled by horse or mule to the furnace site. The limestone was then broken up into smaller pieces for loading into the furnace stack.

The furnaces themselves were constructed of thick, outer sandstone walls with a rubble, sand, and clay lining between the outer wall and inner wall of smaller-sized sandstones. Iron bars helped hold the structure together.  The stacks were usually 30-34 feet in height and were narrower at the top than at the bottom. The iron ore, limestone, and charcoal were loaded from the top of the stack. The hottest area at the bottom of the furnace, near the mouth, was called the crucible.  The slag was released through one pathway and the molten pig iron flowed into prepared sand beds at the bottom opening.  A long central trough, which was formed by the furnace workers in the sand bed, was called the sow trench.  The shorter side troughs coming off the central trough reminded someone of suckling piglets, ergo pig iron.

The bars of pig iron would be used onsite if the ironworks was large enough to have a forge and foundry, rolling mill, and nail factory, or it could be shipped to other markets for sale.  Some castings were also made in the sand bed at the mouth of the furnace by using wooden molds that were pressed into the sand and then carefully removed.

At the chaferies or fineries (refineries), and forges, the pig iron would be reheated and worked by huge mechanical hammers or, at smaller forges, hammer smiths or blacksmiths would hand work the pig iron into wrought iron.  Hammering lengthens the iron fibers and removes the remaining carbon impurities from the pig iron. 

Cast iron is 2-3% or more carbon.  Cast iron is brittle and can break, but it is the best conductor of heat and dampens vibrations.  Cast iron is no longer made, so any cast iron products that are bought today are original pieces or they have been reheated and cast into “new” pieces or reworked into wrought iron products.  Wrought iron contains no carbon and its hardness cannot be increased.

Compiled by Bonnie A. Shockey
November 2004

Resources include: 

Ken Swarz, master blacksmith at the James Anderson Blacksmith Shop, Williamsburg, Virginia; Kittochtinny Historical Society papers; numerous newspaper articles; first person accounts, numerous Websites

Diderot & D’Alembert, L’Encyclopedie Forges, Paris, France

Hartley, E. N., Ironworks on the Saugus, University of Okalahoma Press

Fenstermacher, Shirley B. and McDonnel, Margaret L., Franklin A Frontier County

Soles, Earl L. Jr., Editor in Chief, Colonial Williamsburg Historic Trades, Volume I, The Colonial Williamsburg Foundation, 1988