From Blood and Thunder: The Epic Story of Kit Carson and the Conquest of the American West, by Hampton Sides (Anchor, 2007), Kindle Loc. 4454-4474:
Interestingly, about the same time that the Chaco Phenomenon was imploding, the Navajo began to move into the region. For centuries they had been slowly pushing southward from Alaska and northwestern Canada, working their way down the spine of the Rockies. These nomadic warriors were the epitome of a scattered civilization. Supple, adaptive, refusing to tie themselves down to any one place or way of life, they moved freely with the seasons, following the game or their own whimsy.
When the first Navajo saw the ruins at Chaco Canyon, they must have been stunned. Everything about Chaco represented the antithesis of their own life. The Navajo must have instantly recognized that Chaco culture had been advanced beyond anything they had ever seen. But they also intuitively understood that something terrible had happened here, that this ghost city contained the seeds of destruction. They refused to go into the great houses, believing they were places of evil and death. They would never live this way—in cities, clustered in permanent buildings, trapped in a close environment. They would always leave themselves an out.
The timeline is murky, but it is possible that there was some overlap in the two cultures—that is, that the Navajos flooded in just as the Anasazi were leaving, and that for a brief time they had direct dealings with one another. It’s also possible that the Navajo’s arrival hastened the unraveling of Chaco culture—either through direct warfare or competition for resources. The word anasazi, in fact, is a Navajo word, meaning “ancestors of our enemies,” and it’s a term modern-day Pueblo Indians understandably detest (they prefer the designation “ancestral Puebloans”). Whatever the nature of their relationship, the Navajo clearly filled the void left by the Anasazi departure. They would remain masters of this region, living their roving kind of life in the midst of these crumbling rock cities, incorporating stories about the ruins into their own mythology, but always leaving them alone.
By the time Simpson and Dick Kern wandered through, the Navajo had been the de facto custodians of Chaco Canyon for at least five hundred years. Much of our early understanding of Chaco would be refracted through a Navajo point of view. The word chaco is a Spanish approximation of the Navajo tsekho—meaning “canyon,” or literally, “an opening in the rock.” And even as Simpson had been examining the ruins with his men, Navajo scouts had been watching him from afar, puzzling over his intentions, and possibly wondering whether this bewhiskered little man was a witch.