Credit: Courtesy of Chris DellaMea, www.coalcampusa.com/
Coal was mined in Pittsburgh in the mid-18th Century, and in the 19th Century the Monongahela Valley was dotted with numerous mines. Not many beehive coke oven plants were constructed in the Pittsburgh field. However later on U.S. Steel and Bethlehem Steel owned such mines as Karen, Maple Creek, and Ellsworth. The primary company in this field was the Pittsburgh Coal Company.
