Devils Tower National Monument is the first national monument in the U.S. It was established September 24, 1906 by President Theodore Roosevelt. Devils Tower is an laccolithic butte composed of igneous rock in the Bear Lodge Mountains (part of the Black Hills). It rises dramatically 1,267 feet above the Belle Fourche River, standing 867 feet from summit to base. The summit is 5,112 feet above sea level. The oldest rocks visible in Devils Tower National Monument were laid down in a shallow sea during the Triassic period, 225 to 195 million years ago.
The 1977 movie “Close Encounters of the Third Kind” used the formation as a plot element and as the location of its climactic scenes. Its release was the cause of a large increase in visitors and climbers to the monument.