Chimney Rock rises 470 feet above the North Platte River Valley and stands to the south as the most celebrated of all natural formations along the overland routes to California, Oregon, and Utah. It served as an early landmark for fur traders, trappers, and mountain men traveling from the Rockies to the Missouri River. For 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, but these records disappeared through the forces of nature. The eroded landmark is smaller than the one that greeted early visitors to the area, but its presence for generations to come 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, and in that same year the federal government designated Chimney Rock a National Historical Site.