EAST RIM OF THE GRAND CANYON, Ariz. — Renae Yellowhorse stood at the edge of the Grand Canyon, 26 bumpy miles across the Painted Desert from the nearest paved road, not a glint of civilization in sight. Ms. Yellowhorse, 52, who has lived her whole life on this Navajo land, cast an arm over the gulf sweeping out to the horizon, pointing to where the Colorado River and the Little Colorado meet in a dazzling burst of deep blue 3,000 feet below. “This is where the tram would go,” she said. “This is the heart of our Mother Earth. This...