Devils Tower became the first U.S. national monument on September 24, 1906.
President Theodore Roosevelt issued the proclamation under the Antiquities Act of 1906, which authorized presidents to protect objects of historic or scientific interest on federal lands. The Wyoming formation was selected because of its striking geology and cultural significance.
Devils Tower rises 867 feet from its base to its summit and stands 5,112 feet above sea level. Its columns formed when molten rock cooled and contracted, creating the distinctive vertical pattern visible today.
The name is commonly written without an apostrophe because that spelling appeared in the original federal designation. The site is also known by Indigenous names, including Bear Lodge and Mato Tipila. It is a national monument, not a national park, although both are units of the National Park System.