At the City of Rocks, the two peaks called the Twin Sisters stirred the greatest interest among passing emigrants. An emigrant journal entry by Sawyer, circa 1852, described them as rising in a cone-like form from the bottom of the valley to a height of from 400 to 600 feet, round and quite regular in form, tapering gradually to a point. After months crossing monotonous prairie to the east, travelers found the Twin Sisters sights to behold. Many mentioned them in journals, some sketched them, and in later years photographed them. Although most emigrants saw them as scenic wonders, few, if any, knew that they were geologic wonders as well, for though the two peaks look nearly identical, they are vastly different geologic formations consisting of rocks formed many millions of years apart.