Alderfly family(Sialidae)
larva- 10-25 mm in length. Adult 20 mm. with blackish or dark brown wings. Abundance varies from area to area. only the genus (Sialis) (20 or more species in north america)
taken from Aquatic Entomoligy by: W. Patrick McCafferty
It's not a stone fly, I'm inclined to say caddis,because when I typed alder fly into google all the images looked like caddis to me except a couple. If someone that is an expert tells me it's an alder fly I'd believe them because you just don't see them very often in PA.