Very few hardwoods in North America have leaves that are directly opposite the next leaf. Maple species, which includes the boxelder, is one of the very few where that is the case. Your post of the internet picture of a boxelder shows that pattern. Each leaf is directly opposite another leaf on the leaf stem. Your picture from your own tree shows leaves that alternate from side to side along a stem.
I'm saying mulberry on this one. Bark and leaves look almost identical to a scrub tree my neighbors let grow to a full size. Is it one of the last trees to drop leaves?
I've never heard of a mulberry in these parts, no idea on when it drops its leaves. It's about a half mile back in my woodlot I've honestly never been back there in the winter or fall to take notice.
