The fact that it was recovered in Montana pretty much means
it has to be an American Crow (C.brachyrhynchos). And there's
nothing in the photo to suggest otherwise. Even those who
believe in Northwestern Crow (and the number shrinks daily)
would be hard pressed to defend one from Montana.

Generally speaking, a body length measurement is not much use.
A wing chord measurement (from the bend in the wing to the tip
of the longest primary) and bill measurement (the ridge of the
bill from the place where the bill meets skin to tip) would be
can be checked against values in "Biosystematics of American
Crows" by Johnston.

--
Mike Patterson
Astoria, OR
celata at pacifier.com

If you want to end war and stuff, you've got to sing loud
- Arlo Guthrie