After pioneers journeying west crossed the North Platte River near present-day Casper, Wyoming, many chose to follow a trail that led toward Emigrant Gap and Rock Avenue rather than the River Route to Bessemer Bend and the Red Buttes. An interpretive panel on the Emigrant Gap Route explains that this point — Emigrant Gap — signifies the trail’s departure from the North Platte River Valley and the beginning of the ascent into the Rocky Mountains.
Just a few miles beyond that historical panel is a geological novelty known as Rock Avenue, a site where the trail passed between several ridges of jagged, upended rock. Although it has been noted that it is not known with certainty which option Brigham Young and the pioneer company utilized in 1847 (see "Sacred Places, Vol. 6: Wyoming and Utah," edited by LaMar C. Berrett and A. Gary Anderson, pages 43-44), some journal accounts seem to indicate that this group passed Rock Avenue.
On June 19, 1847, company member Horace K. Whitney wrote that they “noticed huge masses of rock lying beside the road” (see "The Journey West: The Mormon Pioneer Journals of Horace K. Whitney with Insights by Helen Mar Kimball Whitney," edited by Richard E. Bennett, page 274). Other interesting descriptions of this landmark are found in the journals of other pioneers who passed by.
In 1860, travel writer Sir Richard Burton called the feature “the Devil’s Backbone” describing it as “a jagged, broken ridge of huge sandstone boulders, tilted up edgeways, and running in a line over the crest of a long roll of land: like the vertebrae of some great sea-serpent,” according to "Sacred Places, Vol. 6" (page 46).