ONE OF THE interesting challenges about learning history from a Navajo guide is that you're often forced to consider the age-old question "How do we know what we know?"

On another day, Adam and I take off on foot through Canyon del Muerto, and at every turn he shares a tale that, like Ben's story of the defiant woman at Massacre Cave, is based on oral history, passed down in sweat lodges and over campfires. Sometimes Adam tells me the wildest things—about Kit Carson, the Spanish, the Anasazi—things I've never heard even a whiff of before, things I've never seen written down in any books.

Though he's an avid reader, Adam still primarily operates in an oral tradition, and at Canyon de Chelly the stories are out there, on the rocks, along the ground, in the air. He's spent his whole life absorbing them, and retelling them. Sometimes these stories drive me crazy, even as I find them irresistible. The Navajo sense of chronology, often said to be more circular than linear, can be frustrating for a bilagaana writer trying to nail the cold facts to the wall of truth. The what and where details are often precise, but the when is almost always vague.

That doesn't necessarily make them any less true, though; the stories have their own logic and discipline—and an authenticity slowly accrued. Some of these stories are hundreds of years in the making. "We're a patient people," Adam says. "We let things develop."

One day, Adam takes me to see a massive anvil of sandstone called Navajo Fortress Rock and tells me another one of these great mythic stories—maybe the best one of all. Soaring 700 feet and connected to the main wall by only a thin stone bridge sagging from centuries of erosion, Fortress Rock is a legendary place, one that figures prominently in Diné folklore.

In the winter of 1864, Adam says, the Navajo used Fortress Rock as a supreme hideout when Carson's soldiers came pillaging through the canyon. During the weeks leading up to the American invasion, the women stockpiled foods and supplies—smoked turkey, piñon nuts, wild potatoes—while the men made improvements to the old network of Anasazi toeholds, gouging them deeper, so that children and even elderly Navajo could safely pull themselves up.

As it started to snow, some 300 men, women, and children, perhaps tipped off by a sentry that an army was on its way, ascended to the top and pulled up the ladders. Hoping the evil might pass beneath them, they planned to hunker down and dwell in silence for months. Then one day, as the bleak winter sun slipped behind the canyon walls, a column of American soldiers came marching into the canyon, laying waste to fields and chiseling their Kilroys into the sandstone. (Some of their inscriptions are still visible today, and on another day, Adam shows me one.) Somehow detecting the Navajo sequestered on top, the Americans camped near the base of Fortress Rock, beside a stream called Tsaile Creek, and attempted to starve them into final submission.

But unknown to the soldiers, the Navajo were already slowly perishing from thirst; the snows had melted away, and the natural cisterns pocking the surface had run dry.

So one moonless night, the Fortress Rock exiles devised a plan: They formed a human chain along the sloping rock, down to Tsaile Creek, where several American guards lay sleeping. A group of warriors crept out onto a ledge over the stream and dangled gourds from yucca ropes, dipping the containers into the cold running water. They filled gourd after gourd and steadily passed the vessels from hand to hand back up the sheer rock face to the summit. By dawn they had replenished their stores.

So what happened to them? I ask Adam.

"They outlasted the siege," he says. "They were never captured."