An estimated six million people visit the Grand Canyon annually. Most visitors look in from the South Rim or through the window of a helicopter, and roughly 26,000 float the Colorado River through all or part of the canyon. Very few in the recorded history of Grand Canyon exploration have walked its length (fewer than have walked on the moon, Kevin Fedarko tells photographer Pete McBride). Likely no one with the photographic skills of National Geographic photographer McBride have made this arduous journey, which covered 750 miles from Lees Ferry to the Grand Wash Cliffs at the canyon’s western end.