IN THE AFTERNOON of our last day on the Tower, Pat and I climb three classic finger cracks in a row: Carol's Crack, Rain Dance, and One-Way Sunset. My friends, the white-throated swifts, are nowhere to be found. Instead, two prairie falcons, the first we've seen, sail above us in a sky fading to lavender.

We hoped to climb a famous route called El Matador, but the entire west face is closed due to nesting prairie falcons. It's part of Devils Tower policy to protect the falcon and its mating rituals, and every year some 40 routes are off-limits all summer.

The irony isn't lost on the Native Americans, but they're remarkably realistic. For a hundred years, Devils Tower has been an emblem of both the spiritual and the secular, neither of which are absolutes: They're constantly overlapping, subject to personal interpretation and, ultimately, compromise.

On the hike back down through the tall ponderosa pines, I spy a faded blue prayer cloth dangling from a limb. When I first climbed Devils Tower 30 years ago, there might have been prayer cloths in the trees, but I was too self-absorbed to notice. This time is different. Hidden in the branches like Easter eggs, the tiny bundles remind me of the Tibetan prayer flags I've seen in high sacred places across the Himalayas of Nepal, Tibet, and, Bhutan, where I've climbed during all these intervening years.

"Prayer cloths are pieces of calico of different colors—white, red, yellow, or blue—that carry our hopes and dreams, our sorrows and our misfortunes into the sky," Elaine Quick Bear Quiver, 71, tells me later by phone.

Quiver is from the Burnt Thigh clan of the Rosebud Sioux. Her entire life, every June, she and her family have walked to Devils Tower from their home on the Pine Ridge Reservation, in South Dakota. She made her last pilgrimage in 2005, at 70.

"It takes us five days of walking. We go there to pray. My ancestors are buried in the caves beneath the rocks there. I go to give thanks to the Almighty Mystery for helping us through another year."

Quiver was the interpreter for the Native American elders in Liggett's Devils Tower group that suggested the voluntary June closure. Most of these elders are now dead. She and her relatives camp at the Tower, worship on its flanks for four days, and then walk home.

"Bear Lodge is a place to sit and think, to reevaluate your life," she says. "To look at the past and the future. What can I do to make myself better? You sit quietly and ask for help. When you're isolated and alone, you just listen, and the wind will tell you."