stikpusher
Caveman
I believe it's a caribou or even a buffalo.
I’m not familiar with the Buffalo, but after looking it up, yes it could be that also. Apparently the Buffalo is based off of the Caribou. The types of engines used and the placement of the horizontal stabilizers being the main differences. Did it sound like it had radial engines or turboprop engines?
Radials.
I know what a 25 looks like in the sky. I can pick a B-17, B24, B25, A26, B29, HE111 and a Ford tri motor from the ground and I garantee this was not a Mitchell.
John, if there were any HE 117s and they just happen to be flying over Boise, I'd totaly agree.
Stick and Caveman are probably right, something like a Caribou or Buffalo. Two things bother me though, why did it appear (too far for a positive conformation really) to have twin vert stabs and why would it still have radals? On the speed, at a longer distance I thought it might have been a 17 at first. I've seen plenty of those and I had lots of time to get my camera, wait till it was closer then shoot.
It's probably a tanker for the fires but I usually recognize those as well.