Lock Haven is the county seat of Clinton County, in the U.S. state of Pennsylvania. Located near the confluence of the West Branch Susq…Lock Haven is the county seat of Clinton County, in the U.S. state of Pennsylvania. Located near the confluence of the West Branch Susquehanna River and Bald Eagle Creek, it is the principal city of the Lock Haven Micropolitan Statistical Area, itself part of the Williamsport–Lock Haven combined statistical area. At the 2020 census, Lock Haven's population was 8,108.