Devil's slides in Utah and Montana: what were these structures?

Devil's Slide is an unusual geological formation located near the border of Wyoming in northern Utah's Weber Canyon, near the community of Croydon in Morgan County, Utah. The slide consists of two parallel limestone strata that have been tilted to lie vertical, protruding 40 feet (12 m) out of the mountainside. Intervening layers have eroded more quickly, forming a channel some 8 feet (2.4 m) wide running hundreds of feet down the mountain.
  • The Devil’s Slide is now surrounded by private property and access to it directly is not permitted. The Slide is clearly visible from designated freeway pullouts where viewers can also spot many “No Trespassing” signs and other weird objects posted to keep unwanted visitors away.
  • Devil's Slide (Utah) - Wikipedia

Contributing to the strange history of the region, Shriners of the El Kalah Temple of Salt Lake City held ceremonies with thousands of members in attendance and slid down the slide in 1910.

I am not sure how natural this thing is. May be not at all. What do you think. Below is 1860-70s photograph of the same "slide". If it's not natural, what could it be?

Is it considered natural just because we do not need to know certain things? Things like:
  • It might have been possible to construct something like that in the past.
  • The area was occupied by individuals the PTB does not want us to know about.
There is one photographer who could not miss something like this. I'm talking about Mr. Muybridge. The guy "documented" everything we needed to know.


Here is a page with lots of older photographs of this formation.

And then we have another Devil's Slide in Montana located in the area called "Gates of the Mountains", as far as I understand. It looks different from the below engraving these days, but there has to be a reason for that.
  • If it really looked like that, then I have 4 questions:
    • Who built it by 1870?
    • What for?
    • What does it tell us about the "natural" Utah Devil's Slide?
    • Are there more of these?
The Devil's Slide, Montana 1870


Curiously, the article included artwork by Scribner’s chief illustrator, one Thomas Moran, who would later gain fame as one of the principal artists of the 1871 Hayden Geological Survey. Without the benefit of having the feature in front of him, however, his rendition of the Devil’s Slide for Scribner’s (pictured above) is comically artificial, the geologic ridges more like sturdy fortress walls. He would go on to see the Devil’s Slide in person and sketch it (as shown below). Seen one after the other, they make for a curious juxtaposition.


KD: If this formation is not natural, two questions come to mind:
  • Who built it?
  • What was it?