Snuggled along the crest of the Mogollon Rim and stretching 90 miles south, the Tonto National Forest spreads over a spectacular 2.9 millon acres of pine and cactus country just northwest of Phoenix, Arizona. To the north along the Rim country, cool, pine-covered slopes and clear trout-stocked streams attract thousands from the cities when summer temperatures soar. Just over the top of the Rim wooded lakes on the Coconino and Apache-Sitgreaves National Forests beckon hundreds more on weekends. When sun and sizzling urban asphalt push thermometers past the 100 degree mark, only the early birds find vacant Forest Service developed campgrounds.