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Roaring cascades, soaring cliffs, great campsites, and the easiest way to Thousand Island Lake.

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Point to Point

9,568' 2,916 m


8,043' 2,451 m


1,560' 476 m


318' 97 m



Avg Grade (3°)


Max Grade (11°)

Dogs Leashed

Features Commonly Backpacked · Fishing · River/Creek · Swimming · Views · Waterfall · Wildflowers · Wildlife

Family Friendly Not too difficult excursion into the Sierras.

Overnight trips require a wilderness permit. Quota for trailheads (reserved-walk-in): High Trail 20 (12-8), River Trail 30 (18-12). These are very popular trails -- make reservations well in advance. Select Inyo National Forest Wilderness permits. Walk-in permits issued starting at 11:00 AM the day before your trip. They can be obtained at the Mammoth Lakes Visitor Center or the Mono Basin Visitor Center in Lee Vining. No permit required for long (15-mile) hikes.


The River Trail is considered the least scenic way to Thousand Island Lake, but only because we are comparing it to the spectacular High Trail and the John Muir Trail. Without that competition, it would have to be considered a beautiful, exciting trail in itself. Much of the way, it is near the river, which has many roaring falls and cascades. Striped cliffs of metamorphic rock soar high above. Fishing is good, and there are several great campsites where campfires are allowed. It is the easiest trail to Thousand Island Lake. Hikeers often use one of the other two trails to go out and then return via the River Trail.

Need to Know

Numerous streams coming down from the northeast side of the canyon cross the trail and often run down it for a way. Waterproof boots are very desirable.

You can drive to the trailhead in Agnew Meadows, if you arrive before 7 AM. You'll be charged $10 on exit, assuming you leave when the Minaret Road entrance station is open. If you arrive after 7 AM, you must take the shuttle bus. If you have exact change, tickets can be purchase from the driver for $7. Otherwise, they can be obtained from the Mammoth Mountain Visitor Center. The first bus leaves at 7:30 AM.

You cannot camp near the outlet of Thousand Island Lake. Campfires are not allowed at Thousand Island Lake or above 10,000 feet. They are allowed for most of the distance on the High Trail and the River Trail.


The River Trail starts from the second backpacking parking lot in Agnew Meadows, about 0.3 miles from the shuttle stop. It immediately joins the PCT, passes south of the actual Agnew Meadow, and climbs a very low ridge to the edge of the San Joaquin Canyon. At this point, the PCT branches to the left and heads south down the canyon. The River Trail heads north as it descends the canyon slopes to a relatively flat area away from the river. Mosquitoes can often be a real problem from here until you pass the marshy Olaine Lake.

Shortly after the lake and about 2.5 miles from the start, pass the junction with the Shadow Creek Trail #614. The River Trail climbs up the east side of the canyon in two long switchbacks, because at this point the river gorge is too steep and narrow for a trail. You get only a partial view of this gorge, but a great view of Shadow Creek cascading 700 feet down from the Shadow Lake. At 4.4 miles, you'll near the river again and have good views of it most of the rest of the way. At 5 miles, we meet the junction with a trail that climbs steeply up to Agnew Pass and on to Clark Lakes.

At 5.4 miles there is a very large campsite where the stream from Garnet Lake finishes dropping through innumerable falls and cascades to join the San Joaquin River. This campsite is often used by hikers and fishermen who have gear bought in by mule trains. It is an extremely beautiful campsite, but it is often crowded. There is an unmaintained and unsigned trail that climbs from here up to Garnet Lake. The trail is doable, but there is no bridge across the river. This crossing can be a very difficult and dangerous until after the snow melt.

The River Trail continues to climb staying fairly close to the water until it meets the High Trail at 6.5 miles. From there it is only another mile and 200 feet of climbing to reach Thousand Island Lake.

Flora & Fauna

A red fir and lodgepole forest.


Shared By:

Lee Watts

Trail Ratings

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  4.7 from 3 votes
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in California


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3,325 Since Aug 1, 2019
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Cascade on River Trail near a large campsite.
Aug 2, 2019 near Mammoth…, CA



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