That the Commonwealth of Pennsylvania hereby dedicates to the public, for use as a park and pleasure ground for the benefit and enjoyment of the people, all that area of land extending in length from the western city line of Lock Haven, in Clinton County, to the eastern borough line of Emporium, in The County of Cameron, and along the course of the western branch of the Susquehanna River, and its tributary, Sinnemahoning Creek, in Clinton and Cameron counties, an estimated distance of 75 miles , and in width from mountain rim to mountain rim across the valley.