Devils Tower was the first national monument established by the United States under the Antiquities Act.
President Theodore Roosevelt proclaimed Devils Tower National Monument in Wyoming on September 24, 1906. The proclamation used authority granted by the Antiquities Act, which Congress had passed earlier that year to protect historic landmarks, prehistoric structures, and objects of scientific interest on federal land.
Devils Tower is a striking igneous rock formation rising above the surrounding landscape in the Black Hills region. Geologists debate the precise origin of its distinctive columns, but it is widely understood to be the eroded remnant of an igneous intrusion.
The monument’s name is commonly written without an apostrophe in the official federal designation. The site also has deep cultural importance for several Indigenous nations, including the Lakota, who know it by other names and maintain spiritual connections to it. National monuments differ from national parks in their legal origins and management histories.