Rising 470 feet above the North Platte River Valley, Chimney Rock stands to the south as the most celebrated of all natural formations along the overland routes to California, Oregon, and Utah. Chimney Rock served as an early landmark for fur traders, trappers, and mountain men as they made their way from the Rockies to the Missouri River. To later emigrants, the solitary spire marked the end of plains travel and the beginning of the rugged mountain portion of their journey. The tip of the formation is 325 feet above the base. Chimney Rock is composed of Brule Clay with interlayers of volcanic ash and Arickaree sandstone. Thousands of travelers carved their names in the soft base only to have these records disappear through the forces of nature. This eroded landmark is smaller than that which greeted early visitors to the area, but its presence for the generations of the near future is secure. In 1941 the eighty acres containing the site were transferred to the Nebraska State Historical Society by the Roszel F. Durnal family. In 1956 Norman and Donna Brown deeded additional land to the Society. In that same year, Chimney Rock was designated a National Historic Site by the federal government.