Historical Markers
Centre Furnace Historical Marker
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Centre Furnace

Valleys of the Susquehanna


Marker Location:
Porter Road, 150 feet north of East College Avenue (Pa. 26), State College

Dedication Date:
April 29, 1947

Behind the Marker

Photograph of the mansion exterior.
Moses T. Mansion
The layout of Centre Furnace was typical of iron plantations. The furnace stood at the center of the plantation, with a casting house and charcoal house close by. The ironmaster's house, or "big house," workers' housing, and furnace store also were nearby. Farms and ore banks spread out from the furnace, and thousands of acres of surrounding woodland provided charcoal for the furnace.

Construction of the first furnace started in 1791, with the first blast commencing the next year. The furnace stood idle between 1809 and 1826, then produced pig and cast iron for the next thirty-two years. After this cold blast furnace began to function poorly, owners erected a hot blast system in 1847.

Founders were the most skilled workers, responsible for keeping the furnace in blast efficiently. Fillers loaded layers of charcoal through the top into the furnace. Others loaded layers of iron ore carefully so the alternating layers of charcoal were not crushed. The keeper removed large cinders that formed in the molten slag or waste that resulted from smelting the iron, and tapped the slag so that it flowed from the furnace off to one side.

When the founder directed workers to tap the molten iron, guttermen guided the flow of iron into large molds in a sand floor. The flow of molten iron continued into smaller molds attached to the sides of the large ones at right angles. The arrangement of smaller and larger molds reminded ironworkers of pigs (the smaller molds) spread at the sides of sows (the larger molds). Thus ironworkers called the ingots made in these molds "pig iron."
Ruins of the blast furnace at Centre Furnace.
Ruins of the blast furnace at Centre Furnace.

Workers labored in other buildings close by the furnace. At the adjacent cast house, molders and their assistants carried molten iron in ladles from the furnace and poured it into specially shaped sand molds. Molders at Centre Furnace cast stoves and skillets, among other products. Charcoal not used as soon as it arrived at the furnace was piled in the charcoal barn or "coal" house. Similarly, workers dumped surplus iron ore on the ground near the furnace for later use. A blacksmith made or repaired furnace parts and tools in an adjacent shop.

Ore banks scattered over thousands of acres furnished iron ore for the furnace. Miners opened ore banks farther from the furnace as they depleted banks closer to the furnace. By the 1850s miners were digging ore in the Barrens, an area three miles from the furnace. Furnace workers searched continuously for new sources of ore. After "raising the ore," workers rolled horse-drawn, cast-iron breakers over the ore to separate it from clay that clung to the ore. Teamsters then drove horse- or mule-drawn wagons loaded with ore to the furnace. More workers washed the ore with water to remove remaining clay and dirt.

Image of Moses Thompson
Moses Thompson
Many of the workers at Centre Furnace cut or smoldered wood to make the charcoal that fueled the furnace. Woodcutters fanned out into the woodlands surrounding the furnace, going farther and farther a-field to find standing trees. By the 1850s, woodcutters joined miners in the Barrens, bringing trees crashing down.

After cutting the trees, skilled colliers and helpers dug a pit to make charcoal (this was in contrast to general industry practice in which colliers cleared a dry, level place). Colliers and helpers carefully stacked the wood in layers, forming a cone about twenty-five feet in diameter at the bottom. Then they covered the pile with layers of sticks and wood chips, leaves, and dry soil. When the pile of wood was lighted, the covering layers restricted the supply of oxygen, making the wood smolder rather than burn. By smoldering the wood, colliers drove out water and soluble minerals from the wood, leaving carbon. By preventing burning, colliers produced charcoal rather than ashes.

Colliers needed considerable skill to keep the wood smoldering but not burning. Once a collier judged that the smoldering was finished, he choked off all the oxygen, put out the fire, and let the charcoal cool for ten to twelve days. Finally, teamsters drove the charcoal in wagons to the furnace. Driving charcoal to the furnace could be hazardous; occasionally hot charcoal ignited, burning the load and wagon.

Photograph of the grounds and buildings.
Centre Furnace settlement, c. 1912.
Centre Furnace workers kept the fiery blast at the furnace burning until 1858, when the furnace closed forever. The Panic of 1857 and subsequent collapse of the ironmaster's fortune spelled the end of the furnace. The growing distance that charcoal and iron ore had to be hauled raised production costs at a time when Centre Furnace faced growing competition from anthracite-coal and bituminous-coke furnaces.

Over time, much of the former plantation land was developed into the present-day campus of Pennsylvania State University; thousands of students and university employees have replaced the plantation workers that labored there long ago. The Centre County Historical Society acquired the site in 1978, with the restored mansion serving as the society's headquarters and the furnace open to the public.
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