DEVILS TOWER NATIONAL MONUMENT

the first U.S. national monument, established in 1906 in northeastern Wyoming, U.S., near the Belle Fourche River. It encompasses 1,347 acres (545 hectares) and features a natural rock tower, the remnant of a volcanic intrusion now exposed by erosion. The tower has a flat top and fluted sides and is 865 feet (263 m) high. It probably formed when molten rock, pushing upward, encountered a hard-rock layer and was forced to spread into a flat-topped shape. Its colour is mainly light gray and buff. Lichens cover parts of the tower, and sage, moss, and grass grow on its top. Chipmunks and birds live on the summit, and a pine forest covers some of the surrounding country. The monument contains a museum and campground.