Clarion County is a county located in the U.S. state of Pennsylvania. As of the 2010 United States Census, the population was 39,988. Its county seat is Clarion. The county was formed on March 11, 1839, from parts of Venango and Armstrong counties. Clarion County is entirely defined as part of the Pittsburgh media market.GeographyAccording to the U.S. Census Bureau, the county has a total area of, of which is land and (1.5%) is water.Adjacent countiesForest County (north)Jefferson County (east)Armstrong County (south)Butler County (west)Venango County (west)State ParkPart of Cook Forest State Park is in Clarion County.County ParksThe Clarion County Park is located in Paint Township. Clarion County Veterans Memorial Park is located near the Clarion County Courthouse in the center of the Borough of Clarion.