Aerial view looking north at Cheyenne Mountain from an altitude of 10,000 feet above Lytle. El Paso County, Colorado. Circa 1932.

Aerial view looking north at Cheyenne Mountain from an altitude of 10,000 feet above Lytle, Cheyenne Mountain, type locality of the Cheyenne Mountain erosion surface, is a mass of Pre-Cambrian rock that has been thrust eastward onto Cretaceous strata at the south end of the Ute Pass fault. The fault line is marked by the abrupt termination of the foothills. El Paso County, Colorado. Circa 1932. Figure 16, with sketch, in U.S.Geological Survey Professional paper 223. 1950.