Santiago Peak is Orange County's point of highest elevation, offering probably the best urban/mountain/ocean view in all of Southern California. Under good atmospheric conditions, you can trace the coastline from Point Loma to Point Dume, spot both Santa Catalina Island and San Clemente Island, and scratch your head trying to identify the plethora of mountain ranges and lesser promontories filling the landscape inland. Lapping at the foot of the mountain and extending seemingly infinitely toward the far reaches of the Los Angeles Basin are the abodes of some 10 million people.
Don't underestimate the time required to "bag" Santiago Peak by way of the scenic 15-mile-round-trip route described here -- 8 hours (more or less) on foot by way of Trabuco Canyon and the Holy Jim Trail. The total elevation gain/loss on the round trip is about 4000 feet/4000 feet. Take lots of water; there's a trickling spring on the way, but the water cannot be considered potable.
The drive up Trabuco Canyon to the trailhead is an adventure itself, and not one to be undertaken by low-slung cars. Rocks and potholes are the norm on the unpaved truck trail -- Trabuco Creek Road -- going up the canyon. This road intersects Trabuco Canyon Road just east of O'Neill Regional Park in the south Orange County community of Rancho Santa Margarita. Proceed 4.7 miles east on Trabuco Creek Road to the Holy Jim parking area on the left. This is Cleveland National Forest land, so you'll need to display a National Forest Adventure Pass on your car (call 909-736-1811 for more information).
On foot now, proceed north up along the east bank of Holy Jim Canyon's small stream, passing a number of cabins. After bypassing a gate at 0.5 mile, you continue upstream another 0.7 mile, fording the stream several times. Presently the trail switches back sharply to the left, while a lateral trail continues straight, going another 400 yards to Holy Jim Falls -- a worthwhile side trip if the stream is flowing decently.
Our way zigzags upward through dense chaparral on the west slope of Holy Jim Canyon. Soon a few antenna structures atop Santiago Peak come into view, tantalizingly close, but actually about 3000 feet higher. At 2.7 miles, the trail crosses the bed of Holy Jim Canyon at elevation 3480 feet, well above the falls. After another mile on sunny, south-facing slopes, you contour around a ridge and suddenly enter a dark and shady recess filled with oaks, sycamores, bigleaf maples, and big-cone Douglas firs.
By 4.5 miles, you come upon Main Divide Road, opposite Bear Spring. Three more miles of steady climbing on this wide fire road, alternately in sun and in shade, bring you to Santiago's summit. After you arrive you must walk around the telecommunications site to take in the complete panorama below.