LONG AGO AND OFTEN I DREAMED THE BLUE.

Before I walked into and through parts of it, I awoke from it — sleep-drunk on the memory of being lost and found in woods thick and wild.

Then, one October morning, I set into the Blue Range Primitive Area and trespassed back into the dream.

The last of the federally designated primitive areas in the national-forest system, the Blue spans 199,505 acres along the state’s far-eastern edge, cutting a rough spine between Arizona and the Blue Range Wilderness of New Mexico.

Its namesake river flows nearly 51 miles from near Alpine to its confluence with the San Francisco River near Clifton. That river’s valley served as passage for Francisco Vázquez de Coronado and his men as they wandered the Southwest in search of the fabled Seven Cities of Cibola.

Hundreds of years after Coronado traversed Eastern Arizona, naturalist Aldo Leopold learned to “think like a mountain” on Escudilla, the state’s 12th-highest peak. There and within the Blue, he began the slow work of changing public perception about wild...