The Grand Canyon runs 277 river miles and has no trail from one end to the other, so walking it means about 750 miles of route-finding along ledges between the rim and the river, in country where water can be a day apart. Fewer people had done it than have walked on the moon. Fedarko, a former Outside editor who had quit to guide on the Colorado, took it on with his friend the photographer Pete McBride, who sold him on it as a walk in the park. They set out badly overloaded and underprepared, couldn’t hold the pace of the experienced hikers guiding them, and both had to be evacuated in the first weeks. They went back in sections over the following year, and veteran canyon hikers taught them how to move through it. Members of the eleven tribes with ties to the canyon walked stretches with them, which turns the book toward what the park was built on and who was removed to make it.