It looks like sumac to me as well, but not poison sumac. I will admit I've never seen poison sumac in person, probably because its habitat is swamps where I don't tend to hang out. I remember that Samuel Thayer covered it in his first book,
The Forager's Harvest and went to double check. Poison sumac leaves are hairless and shiny with smooth margins. The berries are also distinctly different though the one you have looks too young to have the berries. Apparently it also rarely grows in dense pure stands like the other sumacs.
I would guess that you have either staghorn sumac or smooth sumac. As Mike Jay alluded to, they do grow and spread out into dense, stands. They are also a
perennial edible. I like to keep some around on my property, but I don't let them take hold in the gardens.