In September 1540, Spanish conquistador Garcia López de Cárdenas and a handful of comrades happened upon something no other European had ever seen before: the Grand Canyon. It's difficult to imagine what they must have felt. López didn't keep a journal. We only know that he hurried back from the edge of that chasm as soon as he saw it, gripped with "awe that was almost painful to behold."

Novelist Walker Percy believed that López was not only the first European to see the Canyon. He was nearly the last to see it as it truly is, the last to see it for himself. This is because the explorer—tired and thirsty after a 20-day march across the Colorado Plateau—stumbled upon the gorge with no expectations. He was just trudging along, and there it was.

As for the rest of us, our experience of the Grand Canyon is largely determined by our expectations. Popular culture has immortalized the iconic road trip out West, which invariably includes a stop by the great ...