Prehistoric Trackways National Monument protects 5,255 acres in the Robledo Mountains near Las Cruces, New Mexico, preserving a major concentration of Paleozoic trace fossils in Permian rocks about 280 to 286 million years old. Fossilized footprints and trackways record land animals, sea creatures, and insects moving across ancient coastal or underwater surfaces of the Hueco Seaway, alongside plants, petrified wood, and marine invertebrates. Its modern scientific importance grew after Jerry Paul MacDonald’s 1987 discovery of trackways at the Discovery Site and his excavation of thousands of slabs. Designated in 2009, it preserves an unusually broad record of an Early Permian environment.