Devils Tower is a monolithic igneous intrusion or volcanic neck located in the Black Hills near Hulett and Sundance in Crook County, northeastern Wyoming. It rises dramatically 1,267 feet (386 m) above the surrounding terrain and the summit is 5,112 feet (1,558 m) above sea level.
Also known as Bears Lodge, it is a sacred site for many American Indians. President Theodore Roosevelt proclaimed Devils Tower the first national monument in 1906.
Devils Tower is made of phonolite porphyry. Phonolite refers to the ringing of the rock when a small slab is struck, and its ability to reflect sound. Porphyry refers to its texture, large crystals of feldspar embedded in a mass of smaller crystals.