One of the most important archaeological discoveries of the last century, which rocked the field of archaeology and fundamentally shifted our collective knowledge of human occupation in the Americas. On a warm winter day in 2005, while mending fences in the backcountry of White Sands National Park, David F. Bustos, the park's biologist turned resource-program manager, spotted his first Ice Age human footprint. He initially ignored it as a print made from a modern cowboy boot, but it nagged him for years. As Bustos became adept at identifying the trackways of Ice Age megafauna, he could not shake the feeling that ancient humans had walked there too. It turns out, Bustos was right. With the expertise of archaeologist Daniel Odess, British geologist Matthew R. Bennett, and a vast team of researchers they uncovered what is now considered the longest fossilized footprint trail in the world. Preserved beneath layers of alkaline gypsum sand are the unmistakable footprints of early humans, evidence that rewrites the timeline for the initial peopling of the Americas and is arguably the most important archaeological discovery of the last hundred years. Those Who Walked Before: Fossil Footprints at White Sands is the riveting, first-person account of this extraordinary scientific journey that recounts in vivid detail the excitement of an evolving and ongoing research program complete with dramatic discoveries, disheartening failures, and significant impacts that have shifted our collective knowledge of Indigenous America.