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Ponderosa Pine? The needles look like they're about the right length.

Yes, good job. Your turn! Is there any other reason besides the length?

I'm sure there's some way to do it definitively, but no, that was just a guess based on needle count and length.

Ah, I see.

Hmm, American Hornbeam?

Nope.

Hm, American Beech is the next best thing. I should have guessed that first, the teeth of the American Beech lean forward more.

Nope...this isn't the greatest photo, so here's another shot of the same tree:

That's strange...I've looked through all the trees and still can't find anything like it. I'll take another guess:

Eastern Hophornbeam? It doesn't look terribly like it but I can't think of anything else.

No.

Hint: it's neither in the Fagaceae nor Betulaceae families. The leaf is slightly asymmetric at the base – it's not easy to tell from the first photo, but you can see it in the second photo if you look carefully.

American Elm?