A butte is a geological formation with steep vertical sides or cliffs, a flat top, and a height greater than its width, unlike a mesa, which is larger and has a wider top than its height. Formed when hard caprock such as hardened lava overlies softer rock that is gradually worn away by weathering and erosion, buttes often serve as landmarks because of their distinctive shape. Bear Butte, visible northeast of Sturgis, is a sacred place for Native Americans, with artifacts found on or near the site dating back 10,000 years. The Lakota Sioux call it Matho Paha, or Bear Mountain, and the Cheyenne call it Noahavose, or Giving Hill. In Native American tradition, the Cheyenne prophet Sweet Medicine received from Ma'heo'o on Bear Butte the instructions that govern the tribe's religious, social, political, and economic customs, and the site is still used for religious ceremonies in which prayer clothes and tobacco bundles are tied to trees so the bundles will carry prayers to the Great Spirit. Settlers also used Bear Butte as a landmark during the gold rush. It is a South Dakota state park and was listed by the National Trust for Historic Preservation as one of its top 11 most endangered places in 2011. Bear Butte was formed when magma pushed up from the earth's crust but never erupted, then cooled and hardened over softer rock and topsoil that later eroded away, leaving the formation; because the volcano never erupted, it is not complete. Scientists believe Bear Butte is about 65 million years old, rises 1,253 feet above the plains, and stands 4,426 feet above sea level. If its magma had cooled more slowly, it would be a granite peak. Bear Butte and Devils Tower formed in much the same way and both hold great spiritual significance for Native Americans, but unlike Bear Butte, Devils Tower has a flat top and its more slowly cooling magma formed columns that were exposed as surrounding earth eroded away. Geologists believe Devils Tower formed about 40 million years ago. President Theodore Roosevelt declared Devils Tower the first national monument in 1906, while Bear Butte became a state park in 1961. Devils Tower rises 1,267 above the surrounding plains, stands 5,112 feet above sea level, and rises 867 feet above its base.