The 14,400-acre wilderness, which includes roughly 0ne-fourth of the Sierra Estrella Mountains, is 15 miles south of the metropolitan Phoenix and east of Rainbow Valley, Arizona. Bordered entirely on the north and east by the Gila Indian Reservation, Sierra Estrella Wilderness contains knife-edged ridge-lines, steep slopes, and rocky canyons, one of the most rugged mountainous areas of Arizona. In the northeast corner Butterfly Mountain rises 2,600 feet above the desert plain to an elevation of 4,119 feet in only two miles, a challenge for backpackers and climbers. These extreme elevation changes have produced diverse plant communities: saguaro, cholla, ocotillo, paloverde, and elephant bush lower down, shrub live oak and a few junipers higher up. A remnant herd of desert bighorn sheep roams these mountains. Other permanent residents include the Gila monster, giant spotted whiptail lizard, desert tortoise, mountain lion, mule deer, coyote, javelina, golden eagle, prairie falcon, and Cooper's hawk. Though Sierra Estrella is not far from Phoenix, few humans venture into this Wilderness. If you wander through, you may stumble across evidence of old mining activity. A four-wheel-drive vehicle is required to reach the two public-access points; along the way you'll cross some extremely sandy, deep washes. Primitive dirt roads near the wilderness boundary are extremely sandy or silty and wash crossings are rugged and deep.