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Agnew Meadows to Thousand Island Lake Loop
Trail condition: *****
Distance: 14.8 miles round-trip
Hiking time: 810 hours, or two days
Outstanding features: Incredible glaciated-mountain views, Thousand Island Lake
Set in the geologically outstanding kingdom of the Ansel Adams Wilderness, this popular trail offers day hikers and backpackers traveling on the Pacific Crest Trail the opportunity to enjoy sweeping vistas, excellent swimming at Thousand Island Lake, and a number of alpine-lake side trips along the way.
Starting inside the Devil’s Postpile National Monument area (fee Memorial Day through Labor Day), you’ll pick up the trail at Agnew Meadows, about 4 miles before the Devil’s Postpile information kiosk and gift shop.
From the first of two Agnew Meadows parking lots, start climbing up on the PCT, which heads north just past the outhouses. You’ll ascend approximately 1,300 feet in a little less than 3 miles over sloping fields of mule’s ears and a couple of mature aspen groves. In 2.5 miles from the trailhead, you’ll gain an impressive view of Shadow Lake perched hundreds of feet above the Middle Fork of the San Joaquin riverbed. The lake is nestled in a glacier-carved pot of granite and backed by a ring of jagged, gray spires.
From here, the PCT rolls along nicely, climbing slightly less than 300 feet in a little less than 6 miles beneath the 11,000-foot Two Teats and 11,500-foot San Joaquin mountains on its way to Thousand Island Lake. Overnighters might want to take advantage of a number of side trips along the way. Three different routes to Clark Lakes, a popular destination for anglers, branch off toward the right (north) as the PCT heads in a more northwesterly direction toward Thousand Island Lake. The second turnoff to Clark Lakes is the most efficient route to reach the lakes.
Thousand Island Lake shares a strong resemblance to Lake Aloha just west of Lake Tahoe on the PCT. Each of the lakes is unusually large and littered with smooth, granite islands as far as the eye can see. While Thousand Island Lake takes a little more time to access than Lake Aloha, the trailhead, located just north of the popular Mammoth Lakes region, is just as crowded.
Curiously, many trekkers, laden with overloaded packs, choose to complete this loop by returning south on the PCT. The most efficient and enjoyable way to hike this loop, in my opinion, is to start by going north on the PCT and return heading south on the River Trail. I recommend this direction because you’ll get your climbing out of the way to start with and can finish the trip by descending along the river at the end of the hike.
Approximately 1 mile before reaching Thousand Island Lake, you’ll pass by the intersection with the River Trail. Upon reaching the lake, it’s obvious that the opportunities for exploration are endless. Backed by the impressively rugged Ritter Range, Banner Peak, and Mount Davis, Thousand Island’s shoreline is expansive. This is the headwaters of the Middle Fork of the San Joaquin River, a watershed that rushes freely in the springtime and barely trickles after summer’s gone.
Follow the river’s path on the River Trail as it descends back to Agnew Meadows through dense pine-and-hardwood forest. Along the way, you’ll find a couple of backpacker campsites along the riverbank. Another overnight option is to camp at Garnet or Shadow lakes, which are accessed from the River Trail.
Exactly 1 mile after turning south onto the River Trail from the PCT, there is an unmarked trail that branches off to the right (southwest); follow this trail approximately 0.5 miles to reach Garnet Lake. Approximately 3 miles downstream, a trail leading 1.9 miles up to Shadow Lake (marked) also branches off to the right (west).
The last mile of this loop hike can be confusing to follow. At the first sign and trail junction after the trail to Shadow Lake is a trail that continues to Reds Meadow. Stay to the left (traveling southeast) and continue to Agnew Meadows. Approximately 0.5 miles after the sign to Reds Meadow there is a sign that directs traffic to Agnew Meadows. Keep right at this sign to avoid returning through horse-filled campgrounds.
Directions: Exit US 395 to Mammoth Junction 26 miles south of Lee Vining. Turn west on CA 203/Minaret Summit Road and drive 14 miles to the Agnew Meadows Campground. There is entrance fee Memorial Day through Labor Day. If you’re visiting mid-June through mid-September, there is a mandatory shuttle departing from the Mammoth Mountain Ski Area Gondola Building adjacent to the Mammoth Mountain Inn at the top of CA 203. Due to the volume of traffic, private vehicles are not allowed into the Monument area. At the time of publication, round-trip shuttle fees were $7 for adults and $3 for children. Call the Mammoth Lakes Visitor Center at (760) 924-5500 for details. Overnight backpackers will need to obtain a backcountry permit; reserve in advance by calling (760) 873-2483 or pick up a walk-in permit at the Mammoth Lakes Visitor Center, located at 2520 Main Street in Mammoth Lakes, starting at 11 a.m. the day before your trip starts. More information available at www.nps.gov/depo.
GPS Trailhead Coordinates (WGS 84)
UTM Zone: 11S
Latitude: N37° 40.9700'
Longitude: W119° 5.0722'