The most surprising fact about Arizona's deserts is that their water is made in the cold. Two hundred miles of high country run along the Mogollon Rim — the great escarpment where the Colorado Plateau breaks off and drops as much as two thousand feet to the low country below. Locals call it the edge of the world, and standing on it you understand why: behind you, cool pine forest stretching north; in front of you, the basin falling away toward saguaro and heat. Behind that rim sits the highest, snowiest, wettest corner of the state — and very nearly every river the desert depends on starts up there.
The Rim is one of the great dividing lines on the continent. The largest continuous ponderosa pine forest in North America runs along it, from the country near Flagstaff east to the White Mountains, and the escarpment sorts the living world as sharply as it sorts the rock: species of the Rocky Mountains hold the cool plateau on top, while the plants and animals of Mexico's Sierra Madre climb the warm slopes below. Cross the Rim and you change countries. And because high ground wrings water from the sky — moist air is forced up the escarpment, cools, and drops its load — the Rim and the mountains behind it pull down two or three times the precipitation of the lowlands, much of it as snow. This is the state's rain gauge, and it reads high.
The roof of it all is Mount Baldy. At just over 11,400 feet it is the second-highest mountain in Arizona, an extinct volcano that went quiet two million years ago and stands bare above the treeline, holding snow five months a year. To the White Mountain Apache it is Dzil Ligai Si'an, the White Mountain — one of the four peaks that bound their world, the home of the winds and of the Ga'an, the mountain spirits; the old teaching holds that every wind on earth began here. It is also, in the plainest hydrological sense, a fountain. The two forks of the Little Colorado River rise on Baldy's own flanks; a few ridges south, the White and Black Rivers gather the same snowmelt and join to become the Salt. You can hike the meadows and spruce most of the way up, but the trail stops at a line of rock near the top, because the true summit lies inside the Fort Apache Reservation and is closed to all but tribal members. The mountain is a working watershed and a holy place at once, and the boundary near the summit is not a suggestion.
Follow that water downhill and you reach Salt River Canyon, where the road from Show Low to Globe falls off the plateau in a stack of switchbacks — two thousand feet down to the river and two thousand back up, through a banded gorge Arizonans call the mini Grand Canyon and mean it. The Salt has carried the cold of the high country all the way down here, into a canyon hot enough to feel like a different climate; the river is also a border, dividing the White Mountain Apache's Fort Apache Reservation to the north from the San Carlos Apache Reservation to the south, and you need a tribal permit to leave the pavement. And the Salt does not stop here. Farther down, out of sight of this canyon, it is dammed and metered and sent to the canals of Phoenix — which means the fifth-largest city in the country, down in the Sonoran Desert, is drinking snow that fell on a sacred Apache peak two hundred miles upriver and nearly two miles higher. The desert's water is a mountain's gift, whether the desert remembers it or not.
People have known this far longer than the dams have. On a black terrace of old lava above the Little Colorado, near the river's headwaters, stand the ruins of Casa Malpais — a great house the Mogollon people built around 1260 and lived in until roughly 1400, farming the cold clear water coming down off Baldy. They chose the spot for the reason everyone since has valued this country: up here, in a dry land, there is water. Their descendants are the Hopi and the Zuni, who came back in the 1990s to bless and reseal the burial chambers below the pueblo — proof, if any were needed, that the high country's claim on people is old and unbroken.
The town at the door of all this is Show Low, up on the lip of the Rim at 6,345 feet, where the ponderosa is thickest and the desert state, at last, becomes a mountain one. It is the place you provision before heading for the trout lakes and the trailheads — a threshold town, the last easy stop before the high country proper. It won its odd name in a card game, but its real meaning is elevation: it stands right where Arizona tips from dry to wet, from low to high, from the country that needs the water to the country that makes it.
So the saguaro, the canal, the reservoir, the green lawns of the Valley — all of it is downstream of a cold volcanic corner most visitors never climb, and the few who do are turned back, rightly, at a line near the summit. It is worth flipping the usual picture of Arizona upside down and starting here, at the top, in the snow. This is where the desert begins — not at its hot dry center, but at its cold wet roof.