river formed at Johnsonburg, Elk county, northwestern Pennsylvania, U.S., by the confluence of East Branch and West Branch Clarion rivers. It flows generally southwest for about 110 miles (177 km), past the towns of Ridgway and Clarion, to join the Allegheny River. The Clarion Dam and Reservoir are on the East Branch near Glen Hazel. The river's name is attributed to surveyors who thought its sound, from a distance, was shrill and clear like that of a clarion.