f all the people I talked to about the Red Desert before I hiked into it, Leonard Hay was the most direct. Hay, a vulgar and charming Wyoming native of eighty-seven, is weathered but still tall and quick-witted. He peered at me through thick glasses from where he sat on the flowered couch in his Rock Springs, Wyoming, living room, and said: "It's a harsh sonofabitch."

A few days later, trudging across the Killpecker Dunes, I find it hard to disagree. My eyes are watering in the wind and grit and the hard, bright light. Soft sand tugs at my boots. Plenty of biting flies are finding exposed patches of my skin. I'm looking for elk, but all I see are their droppings, along with small black beetles doggedly making their way across open sand. The dunes are disorienting -- how high, how far? -- and I plod through them and the surrounding bush for several hours, thinking about beer and about what it's like to try to make a living in a place where the dominant features are dirt, rock, and sagebrush.

This vast, windy, dusty swath of southwestern Wyoming called the Red Desert is the classically American desert of the high plains. This is our sagebrush outback. The Red Desert sits atop the continent, where the mountains subside into the surrounding highlands and the Continental Divide -- the line where waters choose between the Atlantic and Pacific -- grows so subtle that in one area it splits in two. At 6,000 to 8,000 feet above sea level, the Red Desert is higher than most places in the country, higher than the Appalachians. It is also, people tell me, the largest unfenced region in the continental United States. It is possible to ride a horse here for three days and never open a gate.

To some people, and Leonard Hay is one of them, the Red Desert's value is in the oil, coal, and natural gas that lie beneath it. Hay has spent his life in Rock Springs (population 19,000), a mining town his grandfather helped found on the Red Desert's southern edge. He is a rancher and an oil and gas developer, and he's proud of the community and economy his family helped build.

"They talk about it being so unique," Hay told me, his voice taking on a righteous tone when the conversation turned to those who want to protect the Red Desert. "I'm a true conservationist, but I'm honest," he said. "I'm for preservation -- hell, I've preserved everything I have. These people, they want to take it for themselves. They would love to get rid of the drilling, love to get everyone off of it."

he Killpecker Dunes look barren at first, but they hide a lot. I come over a rise to find a small sea of vetch blooming purple and white and fecund over a half-acre. Nearby, the wind has uncovered the intact skeleton of a rabbit. Tales abound of human skeletons and artifacts unearthed from the dunes -- a Union soldier, a Ute burial ground, a fully loaded eighteenth-century freight wagon -- most of them wildly unfounded.

Still, surprises and paradoxes are a kind of norm for the Red Desert. I am looking for elk in the sand dunes because elk in sand dunes are about as common as fish on bicycles; almost everywhere else in the country, elk are emblematic of deep forests and high meadows. Even the dunes are an exception here. Most of the Red Desert grows Wyoming Big Sagebrush, which tolerates the combination of ferocious winter temperatures (lows can hit 40 below) and meager precipitation (8 to 14 inches a year). But the Killpecker Dunes are bare sand, a slowly moving stream of it flowing eastward through the sage for 55 miles. Among these creamy folds are seasonal ponds, fed by melting snowdrifts that are buried and insulated under the sand.

The ponds provide habitat for waterfowl, including pintails, teal, and goldeneyes. The Red Desert is also a stronghold for twenty species of raptor and for many plants and animals in trouble elsewhere, such as mountain plovers and swift foxes. Hundreds of wild horses live here. This is also the last, best place, perhaps the only place, where truly free-ranging American bison could ever be reintroduced to the wild.

Given the biological richness here, it's no surprise that Indians used this region for millennia, and it is littered with their artifacts -- petroglyphs, arrowheads, stone circles for vision quests. One site at White Mountain, where the petroglyphs are of animals within animals, is believed to have been a birthing place; handholds worn into the stone may be where generations of women gripped the rock during labor. In the nineteenth century, covered wagons passed through here. The ruts of the Oregon Trail and the Mormon Trail are still visible.

In the Red Desert, where the deer (and elk) and antelope play, where the buffalo might again roam, where Indians and emigrants made homes, an ideological battle is being fought among those who value what is here. Some value what lies on the surface; some value what lies beneath.