can you rule out children?

Yes. No children have lived here since the '80s, and the tree isn't near the property line.

That's a callery pear judging from the fruit. Cut it at the base and apply cut-stump herbicide.

Definitely not a callery pear. Maybe I attached the wrong photo? Since the tree has no leaves the identification photo was an old photo I found in my files...might have gotten them mixed up.

Maybe you did attach the wrong photo, because there is no mistaking those leaves and fruit. Callery pear (at least in the above photo).

Yes, they are large. Not huge...the secondary trunks are almost two feet thick. The trunks are all at least 50 years old. I'm pretty sure the tree is a linden, despite the mistaken uploaded photo.

I have no earth shattering answer, but likely that Maple that came down in a storm had a limb hit parts of the Linden (if that's what it is) and removed the bark, and of course that is going to cause a problem. It seems like a small area in the pic, but, it may be enough for a tree killing bug to set up shop. We had a nice big tree when I was 11-12 years old. I can't remember what kind, but it wasn't an oak. It would've been climbable I think, if it were an oak. But anyway, it was a nice big tree, with the real bark on it. Until we fenced it in with a good bit of land for our horses. All it took was 1 horse with a taste for tree bark. He started chewing a strip of bark, and the tree started declining fast. It wasn't long before the tree was dead. I think the storm making the maple fall and hit this tree cracked the bark up high like that. That is the "easy guess" that may or may not be the answer. But, if the Maple fell about 50 feet away from this tree, or 500 ft away...... just forget what I've just now said Ed.