The Pittsburgh Coal Seam was once recognized as being the most valuable coal bed in the bituminous coal fields of Pennsylvania. The seam crops out at Pittsburgh, thus the Pittsburgh seam is one of forty-two distinct coal beds in the state. No other bituminous seam in Pennsylvania approaches this seam of coal in its overall excellence as a metallurgical coal, which set the worldwide standard. This bed is estimated to have originally contained more than ten billion tons of coal.
The map on the right shows the region known worldwide for “Connellsville Coke,” a portion of the Pittsburgh seam unsurpassed for beehive coking. This remarkable coking coal occurred in a limited area, tucked along the base of the Laurel and Chestnut Mountain Ridges, extending from a point near Latrobe and moving in a southwesterly direction through Westmoreland and Fayette Counties, ending near Smithfield, a distance of nearly forty miles. Located within fifty miles of Pittsburgh, it was the coal that made the coke that made the steel that spurred the industrial expansion of the United States.
The purity of the Connellsville coal bed, as well as its chemical and physical characteristics, made it particularly adapted for coking. The earliest beehive ovens were built in the area surrounding Connellsville before 1845. The coke that was produced from this coal vein was almost 100 percent pure carbon. Connellsville coal was used as run-of the mine coal in the blast furnaces of Pittsburgh without any need to wash it to remove impurities often present in inferior grades of coal; nor was there any need to sort or crush it before the coking process. Chemically speaking, Connellsville Region coal had a low percentage of ash and phosphorus and its sulphur content was less than 1 percent. Being almost entirely free from slate, or other blemishes, no other bituminous seam in Pennsylvania approached it in overall excellence or could compete with it in “cheapness” of production. The seam was of a consistent thickness (7–15 feet) and uniform in quality, remarkably soft, and of superior chemical composition. A 1-foot acre from this area of the Pittsburgh seam was equal to 1,500 tons of coal.
Other coal seams located within the Westmoreland and Fayette County areas include the Waynesburg, Uniontown, Sewickley, and Redstone. These seams, along with the Pittsburgh seam, provided multiple uses: domestic and industrial heating, steam coal, and gas coal used to produce illuminating gas. However, nearly all the coal produced in Fayette County and Southern Westmoreland County was made into the world famous, Connellsville coke and used in the regions steel industry. It earned the reputation as the standard coking coal of the world.
“The Connellsville Coking Coal Fields contain a seam of coal more persistent in its bed and more uniform in quality than any other at present known field in the world. Late science has brought forth a vast knowledge upon coal, and our civilization recognizes it as the material energy of the country, the universal aid, a factor in everything we do.” (Connellsville Weekly Courier, 1914)