I have another picture of a smaller version of the same plant. Is there a way to upload that as well?

Ailanthus altissima, a.k.a. tree of heaven (is this name given ironically?, -- it stinks and spreads like fire).

Thanks. Looks about right so far. Any recommendations for treatment? Also, now that I'm seeing pictures of this menace I realize that I also had a much larger version (essentially a tree) with a base trunk diameter of almost 5 feet across! The tree itself was about 30 feet tall. Is it possible, er likely, that this single root system is responsible for smaller stalks popping up 40-50 feet away???

I don't know where you're located, but it looks like could also be black walnut. Do you have any growing near?

What does the adult tree look like? (pic?) it's probabley the parent either by shoots/suckers or seedlings.