Lieutenant Sitgreaves followed a route that passed north of the San Francisco Peaks, around the south side of Bill Williams Mountain, and then headed west along a corridor that would later be roughly followed by US Highway 66. He crossed into the Sacramento Valley through a pass in the Cerbat Mountains north of Kingman. From there his guide led him across the valley to Union Pass.
Sitgreaves describes the last pass through the mountains before reaching the Colorado River:
“November 5, Camp No. 32.– The approach to the mountains, before alluded to, was by a gradual ascent, so that when we arrived at their base, there did not remain much to be overcome. The pass was nevertheless exceedingly rough, and bordered by overhanging crags, which it was deemed prudent to occupy before advancing with the atajo. We passed through, however, unmolested, and were at length cheered by the view of the Colorado, winding far below through a broad valley, its course for many miles being apparent from the large trees upon its banks. The smoke of numerous fires in the valley gave evidence of a large Indian population, and the sight brought a spontaneous cheer from the men, who believed that this was to be the end of their privations and the labors and anxieties of the journey.”
After reaching the Colorado River near modern Bullhead City and Laughlin, Sitgraeves turned south and followed the river to Yuma.