county, west-central Pennsylvania, U.S., bordered by the Allegheny River to the southwest and Redbank Creek to the south. It comprises a hilly region on the Allegheny Plateau, bisected northeast-southwest by the Clarion River. Clarion county shares Cook Forest State Park with the Pennsylvania counties of Forest and Jefferson. The county was created in 1839 and named for the Clarion River. The borough of Clarion is the seat of the county and of Clarion University of Pennsylvania (founded 1867). The main economic activities are retail trade, manufacturing, and bituminous coal mining. Area 602 square miles (1,560 square km). Pop. (2000) 41,765; (2007 est.) 40,028.