Devils Tower was the first U.S. national monument, established by President Theodore Roosevelt in 1906.
Roosevelt used authority from the Antiquities Act of 1906, which allowed presidents to protect historic landmarks, archaeological sites, and scientifically important objects on federal land. His September 24 proclamation preserved Devils Tower in northeastern Wyoming.
The formation is an enormous columned rock butte in the Bear Lodge Mountains. Geologists classify it as a laccolithic feature, although its exact origin has been debated. It rises 867 feet above its base and has long been a prominent landmark in the region.
The site has deep cultural significance for Indigenous peoples, including the Lakota and other Plains nations, who know it by names such as Bear Lodge. The English name became common through 19th-century military and survey writings. Devils Tower remains a national monument managed by the National Park Service.