Devils Tower was the first declared United States National Monument, established on September 24, 1906, by President Theodore Roosevelt. The Monument’s boundary encloses an area of 1,347 acres (545 ha).
In recent years, about 1% of the Monument’s 400,000 annual visitors climbed Devils Tower, mostly using traditional climbing techniques.
The landscape surrounding Devils Tower is composed mostly of sedimentary rocks. 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.