Historical Markers
Coke Ovens [Bituminous Coal] Historical Marker
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Coke Ovens [Bituminous Coal]

Laurel Highlands/Southern Alleghenies


Marker Location:
Pa. 51 just W of Perryopolis

Dedication Date:
November 22, 1946

Behind the Marker

A "bank" of "beehive" coke ovens in the Connellsville Coke District.
Beehive coke ovens in the Connellsville coke district, circa 1890.
Beehive ovens were critical to making the Pittsburgh-coal seam in southwestern Pennsylvania the nation's foremost coke-manufacturing region during the late nineteenth and early twentieth century. The Pittsburgh seam (see marker First Mining of Pittsburgh Coal) had the best coal in the nation for making coke, which became the principal fuel for iron blast furnaces. At its peak output in 1916, the Pittsburgh seam produced forty million tons of coal. In the same year about 46,000 beehive ovens converted most of this coal into coke. Beehive ovens, belching smoke from smoldering coal, were the standard means of making coke during the period.
Genuine Connellsville coke engraving
"Genuine Connellsville Coke," H. C. Frick Coke Company lithograph, circa 1880.

Coal has been converted into coke since the eighteenth century. To make coke, coal is burned under controlled conditions to drive off volatile matter (gases expelled when coal is burned), leaving carbon and ash from the coal fused together in the form of coke. With its higher proportion of combustible carbon, coke generates more heating power per ton than coal does. Coke is also strong enough to bear the weight of iron ore when both are loaded into an iron furnace.

British iron masters first made and used coke, as early as 1735. In the United States, the first use of coke in an iron furnace occurred about 1817 at markerIsaac Meason's Plumsock puddling furnace and rolling mill in Fayette County. To produce coke for such early iron works, workers piled lumps of coal in mounds, with the lumps placed at sharp angles so air could circulate. Next they covered the mound, usually with turf, and ignited the coal. The covering kept the coal from burning too quickly, so it smoldered instead and the volatile matter "cooked" off. This simple process of making coke took a long time, generally five to eight days. It was also wasteful, converting only about fifty percent of each ton of coal into coke.
 Men working to build a group of ovens.
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Men Constructing Beehive Coke Ovens, southwest Pennsylvania, circa 1900.

Beehive ovens marked a major advance in manufacturing coke. The first production of coke in a beehive oven occurred during the 1830s in Fayette County. Beehive ovens took their name from their dome shape. The masonry domes were constructed in long rows to facilitate loading and unloading. Workers brought coal from nearby mines, dumped coal through openings in the tops of the ovens, and then sealed the ovens almost shut. The coal was ignited and smoldered.

After the coal turned into coke, workers pulled the hot coke out of the domes through front doors, quenched the coke, and loaded it into railroad cars. This coking process took two to three days, considerably faster than making coke in mounds. Very importantly, beehive ovens converted as much as seventy percent of each ton of coal into coke, the rest of the coal being discharged into the air as noxious smoke. Given their significant advantages, beehive ovens largely replaced mounds by the 1860s.

In response to the rising demands of the iron and steel industry, the number of beehive ovens between 1870 and 1905 skyrocketed from about 200 to almost 31,000, which produced nearly 18 million tons of coke in the Connellsville district alone. One observer boasted that loaded into a train, "the year's production would make up a train so long that the engine in front of it would go to San Francisco and come back to Connellsville before the caboose had gotten started out of the Connellsville yards!" The number of beehive ovens in the Pittsburgh seam peaked in 1910 at almost 48,000.
This battery of Coke Ovens includes a danger sign written in six different languages, reflecting the mixture ethnic backgrounds working in the Coke District.
Coke ovens in winter, western Pennsylvania, circa 1900.

The advent of by-product coke ovens in the early 1900s brought the dominance of beehive ovens to an end. By-product ovens, which were made in various designs, captured and recycled the chemical byproducts expelled during coking, including gas, ammonia, light oil, and tar. These chemicals, previously without economic value,  became the foundation of the chemical and plastics industries in the twentieth century.  In addition, by-product ovens yielded more coke per ton of coal, about 74 percent. By-product ovens also could use lower quality coal than that found in the Pittsburgh seam.

These advantages had enormous ramifications for the coal and coke industry in southwestern Pennsylvania. They ended iron and steel companies' reliance on the Pittsburgh seam for coking coal, which triggered the long-term decline of coal mining in the region. They led to the addition of coke ovens at steel mills.

The number of by-product ovens in western Pennsylvania grew gradually, from just a handful in 1894 to more than 2,600 in 1940. With their much greater size, they converted a rapidly rising proportion of the coal mined in western Pennsylvania. In 1915 they used two million tons of coal, or about 6 percent of the total 34 millions tons of western Pennsylvania coal converted into coke. In 1940, by-product ovens consumed 18.4 million tons, or 82 percent of all bituminous coal converted into coke. After World War II most beehive coke ovens closed down.

In 1972 the last beehive ovens stopped operating. Today, in scattered locations across southwestern Pennsylvania, long banks of decaying beehive ovens offer mute testimony to the crucial role these ovens played in the growth of the Pennsylvania iron and steel industries. 
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