The screams of the Suscon Screamer feature in the folklore of Pennsylvania. The Susquehanna Railroad Bridge, now gone, was the focus of the legends. These legends seem to have started around 1900.
Just who or what gave tongue to the screams is a matter of uncertainty. A female ghost has been reported from the area and some ascribe them to her. Another version says there is a lion out there. There has also been a report of Bigfoots.
One of the creepiest reports concerns a creature apparently seen by a hunter. It was a creature 6' long witha long snout and webbed feet. The head of this creature was huge. Although somewhat piglike, it had claws instead of trotters.
There are several versions of the legend. There may be more than one explanation for the screams. From other sources Bigfoot has been reported to scream. If you continue to be curious, there is a great deal of information on the subject on the Web.