Does the tree have simple or compound leaves? Sorry to get all botany geeky here, but that's like near the top of the list that a botanists asks to identify trees and other flowering plants. At the top of the list of botany ID questions is: are the leaves/branches attached opposite each other or alternating along the stem? I don't know if we have resolved this either. This can quickly put boxelder out of contention.
Unlike all other maples I can think of, which have simple (individual) leaves with sharp lobes (or mega-teeth), Boxelder (Acer negundo) is pinnately compound. That means that each leaf is composed of a number of leaflets (where the "compound" term comes from) attached to a stalk (the pinnate part). So the photos are either of simple leaves (then not boxelder) or leaflets of a compound leaf (maybe but not necessarily boxelder). I can't tell which from which in the first image at the start of the thread. A clear image of a few leaves splayed against a uniform background could resolve the boxelder question.
Those are leaflets. I know...it seems petty, but it makes a big difference. See the picture @Bango Skank posted? That drawing contains the image of 1 leaf. There are 5 leaflets, but one complete leaf. take a closer picture of the leaves on the tree if you can. And a better picture of the bark and another of the twigs. Are the 2 trees in the picture different or the same?