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Bufo woodhousii woodhousii
Friendly Frog
These guys are ticky and usually are ID'd by a process of elimination of what they are not. But the mid-dorsal strip, oval parotoid glands and cranial crests seem to sugest Woodhouse's Toad which are common in canyons.
Also add this to the Amphibians of the World mission. Someone there might be able to give you an exact ID. If you call the Ranger District in the area that you found the toad, just mention that you would like to report a wildlife sighting to the wildlife biologist. Great spotting!