Large areas of the Big Woods are seemingly deserted, only visited by an occasional hunter or hiker and of those only the most energetic. But beginning in the 1820s some parts of the Big Woods were a beehive of industrial activity. Throughout central and southern Pennsylvania iron furnaces were constructed to turn iron ore into pig iron for the burgeoning industries of the young country.
The furnaces were pyramidal stone structures with a central chamber which was loaded with iron ore, limestone and charcoal and then ignited. The burning charcoal produced a temperature of 2,500-3,000 degrees which was vital for extracting iron from the ore. It is estimated that an average 19th century iron furnace required the charcoal produced from one acre of woodland for each day’s production. Production of enough charcoal to fuel an iron furnace required a significant acreage of woodland and a substantial labor force.
Take a hike through some sections of the Big Woods and you may find remnants of that charcoal production in the form of “charcoal flats” or hearths. These are flat areas of 25-50 feet in diameter where four foot long billets of wood were stacked,
covered with a layer of leaves, then a layer of soil and
|From PA DCNR|
There was a central chimney in the pile and vents around its base; these vents were opened or closed to control the burn of the smoldering stack – too little air and the fire would go out, too much air and the stack would burn leaving only ash instead of charcoal.
The workers that produced charcoal were called “colliers”, who, with one or two helpers, tended the smoldering wood around the clock for 10 to 14 days until it became charcoal. The collier and his helpers lived in primitive huts, often constructed of poles covered with soil or canvas, and tended a number of piles. Being a collier, although requiring considerable skill, was a dirty, lonely job and colliers were often considered among the lowest of the low.
|From PA State Archives|
When the collier determined that all of the wood had become charcoal the vents were closed, depriving the stack of oxygen and ending the burn. After the charcoal had cooled, which took about a week, the covering was removed the charcoal raked out and loaded onto wagons to be hauled to the iron furnace.
|From PA DCNR|
Only a portion of the Big Woods was affected by the iron industry so it’s not every day that I find an old charcoal flat.
This one was about average in size and a little poking about revealed some left-behind charcoal.
Not far away was an old pitch pine snag – pitch pine lives up to its name as the wood is filled with pitch making it very decay resistant. The snag bore the scars and charcoal of a long-ago fire. It also had an undercut made with an axe when someone in the dim, distant past had begun to cut down the tree. Was the tree burned when the charcoal stack was opened before the charcoal had sufficiently cooled and started a forest fire? Or …?
The iron furnaces that would most likely have been supplied by these charcoal flats were built in the 1820s and ‘30s. Some iron furnaces had a large land base and were able to wait 30-40 years for the areas that were cut first to once again produce trees large enough to cut for charcoal; others were forced to close after all the readily available woodland had been cut for charcoal. By 1850 coal and coke had begun to supplant charcoal as fuel for the furnaces, in part due to charcoal shortage. With the discovery of high-grade iron ore near the Great Lakes and vastly improved transportation the small iron furnaces scattered across Pennsylvania were no longer economically viable and began to close; almost all were out of production before 1900.