About 68 million years ago, during the deposition of the Laramie Formation, this part of North America was a delta with lakes, streams, and a mosaic of swamps, scrubby forests, palm tree thickets, and small open areas. Fossil evidence found along the trail, including impressions of logs, leaves, and palm fronds, indicates a warm, humid climate similar to the Gulf Coast today. As a shallow seaway receded from the continent’s interior, animals here included Triceratops protecting her young from Tyrannosaurus rex, a wading bird, and a mammal clinging to a tree stump, in what would later become Colorado.