US Steel Clairton Works, Clairton PA
Looking across the Monongahela River at the largest coke plant in the country. Bituminous coal from SW Pennsylvania (the Pittsburgh Seam) has long been used for metallurgical purposes, starting with Henry Clay Frick's operations which were folded into Carnegie Steel.
According to US Steel's website -
"The largest coke manufacturing facility in the United States, Clairton Plant operates nine coke oven batteries and produces approximately 4.7 million tons of coke annually, serving customers in the commercial coke market as well as U. S. Steel’s steelmaking facilities."