Thanks @Tetters. Comparing the two trees and looking at the leaves of the second one, I'm inclined to think it's that because of the serrated edge. However, the thorns on the first one seem to match the tree in the images. I'll pass both these on to my daughter-in-law in America - the tree is near her place of work in Ohio.
We`ve been discussing this, and we think it is more likely that the tree with the thorns is a Honey locust as in the first identification, and the ovate serrated leaves have probably fallen from the tree next to it.
It is surprising really that there are so many people on this forum who come from America who seem to be unable to identify a tree that lives there