hmmm - I've changed my mind about this one. The distribution map and the site I use to ID local plants don't show this species out here, but it definitely looks much, much more like this species than Rhus glabra. I see it often, so I'm guessing it was brought out as an ornamental and escaped.
''Rhus typhina'', the staghorn sumac, is a species of flowering plant in the family Anacardiaceae, native to eastern North America. It is primarily found in southeastern Canada, the northeastern and midwestern United States and the Appalachian Mountains, but is widely cultivated as an ornamental throughout the temperate world.