The sky islands scattered throughout the Sonoran Desert help account for its surprising ecological diversity. One such “island” mountain rising from the desert plains is Mount Graham, which rises from the mesquite-studded Sonoran Desert to a height of more than 0,000 feet ( ,0 m). This means the peak has conditions more akin to Canada than to the desert at its foot. Mount Graham was built by a 50-millionyear-long succession of volcanoes and uplift. During the last Ice Age some 0,000 years ago, mastodons, camels, dire wolves, llamas, shortfaced bears, and the humans that hunted them populated the wet southwest region. As the climate warmed, the surviving cold-adapted species were marooned on the mountains and evolved into unique species. Today, Mount Graham and the other sky islands tower over the desert like an ecological ark, hosting five different life zones. The mountain has the highest density of black bears in the Southwest, dozens of different types of trees, hundreds of varieties of birds, and rare creatures like ocelots and perhaps even jaguars.

The mountain bristles with history. Indigenous people have taken advantage of the ability to effectively change seasons by moving up and down the mountain's flanks for at least the last ,000 years. The Apache arrived shortly before the Spanish in the 500s and quickly took advantage of the mountain's resources. Apache medicine men still know the secret places to harvest plants needed in their ceremonies and remedies, which is one reason they believe the Mountain Spirits still dwell on the mountain. The U.S. Army then built Fort Graham at the foot of the mountain and a hospital in a flowergraced meadow atop the mountain to provide suffering soldiers respite from the desert heat. Near the foot of the mountain, Billy the Kid killed his first man, a blacksmith who was bullying the slightly built, light-haired teenager.