The most famous feature of the park, Devils Tower, is a geologic oddity of epic proportions. We share the story of the Tower's formation on our website. Long before molten rock pushed up to form the Tower, other rocks were forming from different origins. Sand and silt left behind by ancient rivers and shallow seas were buried and compacted. Gypsum deposits formed as water evaporated. Creatures big and small - from dinosaurs to clams - left their marks. Today, the stunning cliffs of red and yellow siltstone and sandstone, interbedded with gray shale or limestone and white gypsum, created a multi-colored landscape dominated by rolling fields and dark green forests.