Clarion County was carved out of Venango and Armstrong counties in 1939, and is named for the Clarion River, as is the county seat town of Clarion. The Clarion River was the dividing line between Armstrong and Venango counties.
In early times this river was known as Stump Creek and Toby’s Creek.
These names were retained until an act of assembly was passed declaring it a public highway under the name of the Clarion River.
When surveying for a road, the surveyors camped by the river. They heard ripples of the water made mellow by the wall of timber on both sides of the river. One man said it sounded like a distant clarion. Thense the river was known as the Clarion River.