Devils Tower was the first site designated a United States national monument under the Antiquities Act.
President Theodore Roosevelt proclaimed Devils Tower National Monument in Wyoming on September 24, 1906. The action followed passage of the Antiquities Act, which Congress enacted that year to protect archaeological sites, historic landmarks, and objects of scientific interest on federal land.
Devils Tower is a striking igneous formation in the Black Hills region. It rises about 867 feet from base to summit and is often described geologically as a laccolith or volcanic neck. The formation is sacred to several Indigenous peoples, including Lakota communities, and has long-standing cultural significance that predates the national-monument designation.
The name “Devils Tower” came from nineteenth-century non-Indigenous usage and has been debated because of translation and naming issues. It is also easy to confuse the monument with a national park. A national monument can be established by presidential proclamation under the Antiquities Act, whereas national parks generally require an act of Congress.