In 1891 Dr. E. H. Barbour, Director of the University Museum (1891-1941), led the first University of Nebraska fossil hunting expedition to the Fort Robinson area shortly after the Battle of Wounded Knee, and since that time the Museum has had field exploration parties in western Nebraska nearly every year.

In order to associate the sciences of vertebrate paleontology and geology, the exhibits in the Trailside Museum have been arranged in a chronological order relative to the fossil-bearing deposits of the Pine Ridge area. Invertebrate fossils, ammonites and other typical forms, from the Cretaceous deposits (60-130 million years in age) represent the older fossil beds. Artifacts of late "Ice Age" man and the skulls of bighorn sheep and bison are displayed from the more recent deposits.

During the latter part of the "Age of Dinosaurs" most of Nebraska was covered by a great inland sea. The Mosasaur, a giant sea lizard which sometimes attained a length of 35 to 40 feet, swam in this sea. The Plesiosaur, an aquatic reptile nearly 50 feet in length, also lived during this time. Remains of dinosaurs have been collected from adjacent states. Skeletons of the world famous Triceratops (three-horned dinosaur) were found only 80 miles north and west of Fort Robinson near Lance Creek, Wyoming. Examples of these prehistoric marine and land reptiles are shown in the Museum.

The strange erosional features which occur in the Nebraska Badlands northwest of Fort Robinson have long been a subject for research and discussion by geologists and naturalists. N. H. Darton, a pioneer geologist with the U. S. Geological Survey, gave the name "Toadstool Park" to a locality where ancient river channel deposits of Oligocene age are exposed. For many years this area had been difficult to reach by automobile, until a road was constructed, and the National Forest Service, aided by other agencies, provided picnic ground facilities. Large photo-murals of the "toadstools" and other physiographic features may be seen at the Trailside Museum.