The Sunset Ridge Trail is a short, 0.3-mile loop adjacent to Deer Flat Campground that leads to a scenic viewpoint. Adjacent to Deer Flat, 1.2 miles from, and 600 feet in elevation above Crystal Lake Campground, the panorama includes sweeping views of the San Gabriel Canyon, the San Gabriel Mountains and beyond.
The San Gabriel Canyon is enclosed to the east by Windy Gap (7,588 feet), South Mount Hawkins (7,782 feet), Pigeon Ridge, and Burro Peak in the distance. The Santa Ana Mountains loom on the horizon. Behind is Mount Islip (8,251 feet), whose ridge encloses the canyon to the west. At the base of South Mount Hawkins and Windy Gap are Alexander Spring and Big Cienega alongside the winding course of Crystal Lake Road to the eponymous lake and campgrounds.
The San Gabriel Mountains are known as a Transverse Range, a geological feature of Southern California created by the tectonic action of the Pacific and North American plates. Millions of years ago, as it trudged northwest along the West Coast, the Pacific Plate tore off a slice of the North American plate, rotated it 90 degrees, and began to squeeze. This ancient rock of the North American plate, now oriented east-west, began to rise, as it still does, into the San Gabriel Mountains. Without the San Gabriel Mountains, Los Angeles would be climatically unrecognizable: the mountain range traps cool, moist Pacific air and blocks the hot, arid air of the interior west, preventing desertification. Such conditions allow a range of flora and fauna to flourish. Along the rivers of the San Gabriel Mountains are groves of willow, cottonwood, sycamore, and alder. A subspecies of the Leather Oak grows here, the only place in the world it can be found. There are groves of ponderosa pine and madrone. The mountains are home to bobcats, mountain lions, bears, hawks, and the rare eagle or California condor, all within 50 miles and a five-minute walk of Los Angeles.