Barking, Pa. - home of the Oakmont Mine - was opened in 1917 by Diamond Coal & Coke Co. Later it was operated by Hillman Coal & Coke Co., then it became a captive mine of Wheeling-Pittsburgh Steel Co. A Sept. 11, 1933 explosion in the mine killed seven people.
Sources:
http://patheoldminer.rootsweb.ancestry.com (now defunct) by Ray Washlaski. Accessed here through the Wayback Machine.
Pennsylvania Mine Map Atlas, www.minemaps.psu.edu/.