Isolation defines the Big Bend today. The border town of Presidio, and the surrounding river valley, can seem especially remote.

But along the roads here, on riverbanks and in nearby canyons, ruins and traces tell a different story.

The Presidio Valley is La Junta de los Rios – the confluence of the Rio Grande and the Rio Conchos. And a few centuries ago, it was a hub of Native American life, a center in a complex interplay of diverse societies.

Big Bend prehistory is closely associated with hunter-gatherers. For more than 10,000 years, nomadic peoples hunted game and harvested desert plants.

In the 1940s, Texas archeologist J. Charles Kelley began to study the Presidio area. W...