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I think it is an elm tree. At least that is what the leaves look like to me.

Ooh, with that in my head I pulled out the Audubon book I have and I think it's a Siberian Elm, which would be REALLY prefect for my area.
"Habitat: dry regions, tolerant of poor soils and city smoke, also scattered in most soils along streams."
Yay! I think that's it! Thanks for the hint!

No problem!