Each step that an elk, mule deer, or pronghorn takes during its migration leaves a mark on the land. The tracks may be ephemeral, but together they become corridors that are passed down from generation to generation, sometimes for millennia. This book examines the traces of animal migration in Wyoming, from a tintype of a columbian mammoth tusk, to the lost migration of bison on the Laramie Plains. The book concludes with stories of conservation in the living migration corridors of the Green River Basin, with a portfolio of images showing human and animal trails across Wyoming. The book features two portfolios of images by Bailey Russel, one set from Nicole Jean Hill, and two natural history essays on migration by Gregory Nickerson. Produced through the 2017-2018 University of Wyoming Interdisciplinary Seed Grant, with support from the Wyoming Migration Initiative.