The accumulation of wind-blown sand into a dune marks the beginning of one of Nature's most interesting and beautiful phenomena. In addition to the remarkable structure and patterns of sand dunes, they also provide habitats for a variety of wildlife. The arid regions of the southwestern United States contain a vast variety of dune systems. Visit three groups of sand dunes located on public land in the United States. First, explore a set of dunes that sit at the foot of the Rocky Mountains in Colorado and are fenced in by two river systems complete with stands of Aspen trees. Learn how these river boundaries affect the nearby dunes and inspect the insects that call the dunes their home. Next, travel to the base of the Guadalupe Mountains in west Texas where a tiny gypsum dune system plays host to wildflowers on its edges and rodents living within. Finally, visit White Sands National Monument in New Mexico and examine ancient hearths built by Native Americans who made the trek to the dunes to escape the harsh mountain winters.