Adventure Pass required to park at trailhead. Camping is allowed only in designated sites.
This loop begins at the lower parking lot for Crystal Lake which serves as the trailhead for the Islip Ridge Trail #9W08
. From the southwest corner of the lot, follow the dirt trail as it passes the lake and begins the long climb up to the main ridge and enters a Jeffrey Pine forest. There are fine views of the San Gabriel Wilderness to the west and on a clear day it is possible to see downtown LA and the Channel Islands. As the trail climbs, the forest cover thickens and the temperature drops dramatically.
After four miles a junction with the Big Cienega Trail #9W07
is reached. Hikers short of time or energy can take this trail down to the Windy Gap Trail #9W06
and complete the remaining part of the loop saving two miles and 600 feet of gain.
Those who continue on up will be rewarded with outstanding views of the Mojave Desert and surround high peaks. The trail climbs a rocky ridge with rare ancient Limber Pines then meets with the Mt. Islip Trail #9W05
. Turn left and proceed 0.2 miles to the top of Mt. Islip where the foundation of an old lookout tower can be seen.
After a well-deserved rest descend on the Mt. Islip Trail #9W05
heading east along the ridge and passing the junction with the Islip Ridge Trail #9W08
. This is a good opportunity to stop and take in the unique geology that formed the large basin to the south. While the north slope is more gentle and forested, the south slope is barren and steep. A series of massive slides from Islip Ridge to Hawkins Ridge filled a deep canyon creating the horseshoe shaped basin. Deer Flat directly below the peak contains the former top of a much higher Mt. Islip.
In less than a mile there is another fork. The right trail drops directly down 0.2 miles to Windy Gap. A scenic alternative that adds 0.3 miles is to continue on the Mt. Islip Trail #9W05
to Little Jimmy Campground. Head through the shady campground, popular for scouts and Pacific Crest Trail (PCT) through-hikers, then pick up the PCT east for 0.3 miles to Windy Gap passing Little Jimmy Spring which has good water all year. In summer, the spring is adorned with bright yellow lemon lilies.
From Windy Gap descend the popular Windy Gap Trail #9W06
1.4 miles to the South Hawkins Road #3N07
. The Curve Fire (2002) burned more intensely on portions of the slope where the gap formed a natural chimney intensifying the heat. Turn right and follow the dirt road 0.6 miles on a gentle surface to Deer Flat passing a lush spring (Big Cienega) along the way. Bighorn sheep often pass over Islip Ridge and graze the area around the springs. At Deer Flat there are several large group camping sites. Turn left on the paved road for 0.1 miles then turn right at the lower camp site to reach the Lost Ridge Trail #9W25
. Deer Flat Group Campground has unfortunately remained closed (as of 2018) due to budget cuts and concerns about fire.
Continue on down the Lost Ridge Trail #9W25
as it passes though thick chaparral of oak and ceanothus then drops more steeply entering a nice section of pines, bigcone spruce and oaks. The "lost" ridge was actually part of Islip Ridge that slid down forming Deer Flat and Crystal Lake. It soon ends at the junction with the Lake Trail #9W27
. The left fork passes through a nice oak canopy to the main campground, store and Visitor Center in 0.3 miles. Take the right fork to reach the Crystal Lake parking lot and picnic area in 0.3 miles.
From the lower parking lot descend the steps down to the lake and then take the dirt road on the left (east) side of the lake enjoying views of the only natural lake in the San Gabriel Mountains. There is no outlet and water seeps from the bottom of the lake out to springs along Highway 39. In dry years, the water level can be very low.
Continue on the dirt road as it passes through a pine and oak forest and ends at a locked gate next to the trailhead. Reward yourself by stopping at the Crystal Lake Store and Cafe for refreshments.
High alpine forest around Mt. Islip includes Jeffrey and sugar pines, white fir. Lower elevation has live oaks, bigcone spruce. Bears, deer, foxes, squirrels are commonly sighted. Bighorn sheep can sometimes be seen on the higher slopes around Big Cienega. Rattlesnakes commonly seen in summer on lower trails. Nice wildflowers in spring.