Thanks for the quick reply.I forgot to mention it has red leaves in the late summer/early fall,and produces purple berries.
Could be Prunus padus, but I'd think Prunus virginiana is far more likely (looks very similar, and is native in your area).
I believe it is a purple chokeberry,see: http://en.wikipedia.org/wiki/Black_Chokeberry although I am not an expert.My late mother was particularly fond of it.
