An Ancient World
About the time that the finishing touches were being put on Wind Cave, visitors to the place we call Wind Cave National Park would have seen a completely different world. The geological time period was Oligocene, which extended from about 34 million years ago until 23 million years ago. The Great Plains were just beginning to develop. Dense deciduous forests were becoming open wooded grasslands. The climate was subtropical and gradually became cooler and drier over a long period, transforming the vegetation of the Earth to something far more like that of today. These changing environments had a dramatic effect on the lives of mammals around the world.
The Land Changes
Mammals, which blossomed with the disappearance of the dinosaurs, were expanding both in range and in variety as land bridges between the continents allowed them to invade new territory. Here in South Dakota, the Great Plains was a rich environment where many animals, ones we would identify as quite unusual, lived their lives.