Rising high above the town of Mammoth in California’s Eastern Sierra, the Ansel Adams Wilderness contains some of the nation’s greatest unspoiled wild areas. Bisected by both the John Muir Trail and the Pacific Crest Trail, this area has some absolutely stunning scenery, and the highlight of the whole thing might be 1,000 Island Lake.
While this lake probably doesn’t actually have 1000 islands, 1000 Island Lake does have quite a few! More impressive though is the stunning Ritter Range just behind. When you think of impressive mountain scenery, panoramas like this are what comes to mind! Despite the stunning beauty, 1000 Island Lake is rarely visited as a day hike because of the 18 mile round trip journey. We decided to go for it anyway!
Miles/Elevation:
18.4 miles
4,177 feet vertical gain
About Inyo National Forest:
At nearly 2 million acres, Inyo National Forest is a massive area of soaring peaks, desert, ancient forest, and incredibly rugged alpine terrain. Inyo contains the Big Pine Lakes, Mt Whitney, the lower 48’s highest peak, along with some of the world’s oldest living things, the ancient bristlecone pines.
Covering large swathes of the Eastern Sierra Nevada and White Mountains, as well as much of the Owens Valley, Inyo National Forest actually is one of the least forested national forests in the country. There’s lots of desert terrain here! First protected by president Theodore Roosevelt in 1907, the forest was initially created to facilitate the creation of the Los Angeles Aqueduct.
Nowadays, Inyo National Forest is much more well known as a world class outdoor destination. With renowned wilderness areas such as the Ansel Adams Wilderness, the Golden Trout Wilderness, and the John Muir Wilderness, many of the best backpacking routes in the country pass through Inyo.
In addition to backpacking, there are many other amazing locations in Inyo National Forest that can be easily accessed in a day, either by hiking or by car. These include Mammoth Lakes, Convict Lake, the Ancient Bristlecone Pine Forest, June Lake, and Mt Whitney.
Much of Inyo National Forest does not require fees for day use, though some limited access locations may require fees. There is no fee to park this trailhead!
About the Ansel Adams Wilderness:
Split between Inyo National Forest, Sierra National Forest, and Devils Postpile National Monument, the Ansel Adams Wilderness is an extensive area of protected land in the Sierra Nevada. Named for the acclaimed wilderness photographer Ansel Adams, this region contains some of the most impressive scenery in the entirety of the Sierra Nevada.
While the mountains here aren’t as high as many of the peaks in the neighboring John Muir Wilderness, the highlights of the wilderness are visually just as stunning. The highlight here is the Ritter Range, a jagged, darkly colored range of peaks running right through the Ansel Adams Wilderness. There isn’t a more ruggedly beautiful stretch of mountains anywhere in California!
This wilderness is known for its hiking and backpacking, and at over 232,000 acres and 349 miles of trails, there is plenty here to explore! Both the legendary John Muir Trail and the equally legendary Pacific Crest Trail pass through this wilderness area, but there are many shorter day hiking opportunities as well!
The Ansel Adams Wilderness sees very high usage, so use is limited in many cases. Permits are required for all overnight travel. Trailhead access in Devil’s Postpile is limited. Secure, bear proof storage, is required for food items in certain areas of the wilderness. Campfires are also prohibited above treeline as well as around certain water features. Be sure to adequately research any trip you take into the wilderness!
About Mammoth:
Located on the eastern edge of the Sierra Nevada, Mammoth is a small mountain community known for great skiing, alpine lakes, and world class hiking. The town itself, Mammoth Lakes, named for the numerous nearby lakes, has about 7,000 people, and is one of the largest communities for hours in any direction.
At around 8,000 feet of elevation, Mammoth lies just above the desert treeline. Head out of town and within a mile you’ll be in the scrubland of the high desert. Head towards the high peaks of the Sierra and you’ll very quickly enter the alpine pine forest!
Mammoth Mountain is home to the area’s top ski resort. At just over 11,000 feet, this volcanic complex gets great snow in winter, and in the summer is converted into a mountain biking mecca!
Above the town, the Mammoth Lakes Basin offers tons of camping and outdoor recreation. Situated around Lake Mary, Lake George, Horseshoe Lake, Twin Lakes, and others, campgrounds like Coldwater and Lake Mary provide hundreds of wooded sites. Just don’t expect much for phone coverage up here!
Getting To Mammoth:
The first challenge in getting to this trailhead is to get to the Eastern Sierra. The closest town is Mammoth Lakes, and that will be most people’s base camp when visiting Heart Lake.
Located in the high desert of eastern California, Mammoth is a surprisingly remote place considering it’s in California. The closest sizable city is Reno, about three hours to the north. Los Angeles and Las Vegas are both a bit over 4 hours away, and the Bay Area is about 6 hours away.
The main highway to access Mammoth and the broader Eastern Sierra area is highway 395. 395 runs from just north of the Los Angeles area all the way north to the Canadian border. Reno to Mammoth is a straight shot down 395, and Los Angeles is a straight shot north on 395.
There are a couple of small airports in the area, namely Bishop and Mammoth Lakes. However, commercial flights are either sporadic or non-existent. Driving from a larger metro is the easiest way to access the Eastern Sierra for most.
Getting To The Trailhead:
Hike to Ediza Lake for an up close view of the Minarets and Ritter Range!
Take 395 to the June Lake Loop, highway 158, just a few miles north of Mammoth. Follow 158 to basically the far end of the loop near Silver Lake. Just to the north of Silver Lake itself, turn into the trailhead just across from Silver Lake Campground. There is a large circular parking area at this trailhead.
Tips:
- This hike can get really hot. Bring more water than you expect to need.
- It doesn’t look like it on a topo map, but there is a fair amount of climbing on the return trip.
- Hike clockwise. This will get most of the climbing out of the way early on.
- Wear bugspray.
The Thousand Island Lake Trail:
To Agnew Lake:
From the parking area, begin hiking on the Rush Creek Trail heading south. The trail doesn’t seem like much to begin with. You’ll pass a RV park, cross a stream or two, and then head through a stand of trees behind the Silver Lake Resort. Once you pass the resort and emerge near Silver Lake itself, the hiking drastically improves.
Once you pass the resort and emerge near the highway, the trail takes a steep turn up! From here, the climbing essentially does not stop until you reach Agnew Lake!
The views immediately begin opening up. Silver Lake will quickly be visible in full. Reversed Peak across the valley will be a constant presence for the first couple of miles. And in front of you, Carson Peak dominates the skyline.
While the views on their own are awesome, the hiking itself is excellent too. The trail to Agnew Lake spends its entire time climbing up and out of the valley holding Silver Lake. For most of that time, you’ll be right on or close to the edge.
First you’ll have hundred foot drops, then a few hundred feet, and then towards the top you can look nearly straight down for over 1,000 feet! Exposure definitely makes each step more exciting!
Convict Lake is a stunning place to hike just outside Mammoth!
You’ll eventually come across a railway that seemingly goes straight up the side of a mountain. I wasn’t quite sure what I was looking at when we hiked here, but there is actually a substantial amount of hydropower infrastructure up here. Agnew Lake is actually a reservoir, something I was completely unaware of, and the rail line is for servicing all that stuff!
Cross the tracks (you’ll cross them again before you reach the lake), and continue climbing. Once you reach the tracks you are on the upper half of the climb to Agnew. Towards the top, the trail enters some pretty sheer cliff bands, and the drops become even more pronounced than they have been!
Check out Heart Lake for an easy hike in Mammoth!
Continue up the switchbacks, and before long the trail will actually begin to level off! Once the trail levels off, this means you are leaving the valley that contains Silver Lake below and entering the valley holding Agnew Lake above! Continue straight past a bit of infrastructure, and you will encounter a… dam?
You may have figured this out by now, but I was pretty surprised to discover Agnew Lake is actually a reservoir, but you learn something new every day! You’ll hit an intersection where you can either continue straight or turn left just below the dam. Turn left here.
You will pass a bit of hydropower infrastructure before reaching the base of the dam. Just below the dam, the trail turns to the left and enters into a dense stand of trees. Push through the trees for about 5 minutes and then emerge above Agnew Lake.
Agnew Lake isn’t the idyllic backcountry lake that I was hoping for, but it’s still a nice view. The lake is nestled in a steel walled valley, and beyond the water the other trail is visible a fraction of the way up the opposing mountain! It’s a nice view, but we didn’t even stop here!
To The Clark Lakes:
Once above Agnew Lake, continue on. In front of you is a large talus slope leading up and to your left. It may look like a mess, but that boulder field is in fact where you’ll be going.
Emerald Lake is another nice and easy hike in Mammoth!
The trail through the boulder field actually is very well made, and while it is quite rough and rocky, progress comes easy. This isn’t a scramble, it’s a hiking trail, which might be hard to believe when this slope is viewed from afar!
The slope is very steep and the switchbacks leading up are unrelenting. Continue pushing though and you’ll eventually emerge in a lovely valley. I was not expecting a valley up here, I thought we would crest a pass and then descend the other side, but in fact there is a very nice hanging valley above Agnew Lake!
The trail passes through the valley and then quickly begins climbing up its right side. We were pretty beat by this point. To reach the valley you have to climb about 2,300 feet, and we still hadn’t stopped for any food or water!
The Mammoth Crest Loop is one of the best difficult hikes in Mammoth!
We pushed on and ascended up the right side of the valley. Again, I expected to crest a pass, but again we were greeted by another valley. Continuing right, now out of the first hanging valley, we hiked for another quarter mile or so, gently climbing through yet another valley.
Finally, we reached a pass! The pass up here doesn’t have a name that I could find, but it’s magical! For one, I was so relieved to finally be done climbing! By now, we had climbed about 3,000 vertical feet in 4 miles or so! However, the true pay off were the views!
We had really nice views the entire day up to this point, but we weren’t able to see the high peaks of the Ansel Adams Wilderness. From up here, we finally could! In the distance the horizon was defined by the jagged edges of the peaks, and while the view was nice, we knew there was still a long way to go to actually reach those peaks!
From this first pass, the trail begins a gentle descent down towards the Clark Lakes. There are numerous small lakes that collectively are known as the Clark Lakes, so I couldn’t really tell you what lakes specifically we saw here.
Driving up 395? Make sure you have the Top Down Lifestyle playlist!
The Clark Lakes are very nice, albeit small, alpine lakes. They aren’t really anything special, but they make a nice landmark on the hike! You’ll first pass a round lake on your left. Just past this first lake, turn left at the intersection. A quarter mile later, you’ll arrive at another of the Clark Lakes. Then just past this one, there’s a small one!
At this last Clark Lake, you’ll be standing above the PCT looking down into a canyon. Continue forward to descend down to the PCT in the canyon!
To 1000 Island Lake:
From the last of the Clark Lakes, you’ll immediately have a 350 foot descent to navigate down to the PCT. The trail here is a bit steep and a bit slippery, but progress comes quickly as the trail really isn’t that bad.
At the bottom of the hill, take a right to continue onto the PCT. If you aren’t aware, the PCT is a cross country route that travels from the Mexican border and the Canadian border. This hiking superhighway will likely be much busier than any of the trails thus far, so be ready to meet some neighbors.
From the intersection with the PCT to 1000 Island Lake is a bit under 2 miles. The first mile of this will see you on a general incline, albeit a very shallow incline. After the first mile, the climbing picks up a bit as you approach 1000 Island Lake. The last mile approaching the lake only requires about 250 feet of climbing, so nothing crazy still!
The approach to 1000 Island Lake takes you through a rugged region of rolling granite hills. The trail gets a bit rougher, but in front of you, rising above the local rock formations, the legendary peaks of the Ritter Range rise dramatically, giving evidence and providing encouragement that you’re approaching the lake!
After rounding a corner and cresting a hill, the waters of 1000 Island Lake will present themselves to you! Standing proudly in the background is Banner Peak, and in the foreground are the crystal clear waters of 1000 Island Lake! Again, doubt there are 1000 islands, but you’ll notice quite a few!
Always follow basic trail etiquette when you’re hiking!
I had been looking forward to making it to this lake for some time, and upon arrival it really did live up to the hype. Banner Peak isn’t the highest mountain in the world (it’s not really even that big for the Sierra) but the way it dominates the skyline here is incredible. The rest of the Ritter Range forms the skyline from left to right, and the lake itself is beautiful too.
I definitely see why this is considered one of the highlights of the PCT, and we thoroughly enjoyed our time here!
To Gem Lake:
After a long rest break with lots of water and snacks, we packed up for the return journey. One awesome thing about this hike is that it’s mostly a loop! Technically it’s more of a lollipop. There would be some stints on the trail we had already seen, but we would largely be on fresh trail. There was still another lake to see too!
From the shores of 1000 Island Lake, retrace your steps along the PCT for just over a mile, climbing moderately as you go. Around a mile after departing, take a left to head up to the Clark Lakes. Note: this is not the trail you took from the Clark Lakes down to the PCT. This is a different trail, and you’ll reach this one before you would reach the previous trail.
One of the bummers about this hike is there is a substantial amount of climbing on the hike out, and that manifests itself here. From your low point on the PCT, there is about 300 feet of climbing to do before reaching the Clark Lakes. It isn’t anything all that crazy, but you’ll probably be feeling a bit worn out by now!
At the top of the climb you’ll emerge at a pair of the Clark Lakes. Follow the trail as it passes between two of them, and then at the intersection on the far side of the lakes, turn left to head towards Gem Lake. The trail to Gem Lake is not the most direct route back to the trailhead, but Gem Lake is worth seeing!
From the Clark Lakes, you’ll have about 2.5 miles of hiking and 700 feet of descending to do before reaching the shores of Gem Lake. The trail here is really nice and makes for wonderful hiking, and you’ll pass through a well made set of switchbacks on your descent.
The trail actually goes almost all the way around Gem Lake, so if it feels like you should be close to the lake, you probably actually are! There is just a big hill between you and the water!
Mammoth is bear country so make sure you’re bear safe!
As you approach Gem Lake, you’ll pass a few small lakes and ponds, as well as cross the crystal clear Rush Creek. Across Rush Creek, there is a super annoying little 110 foot climb. That’s nothing in the grand scheme of things, but just getting this far is a ton of work, and climbing this deep into a hike should be criminal!
After that little kicker of a climb though you will begin approaching the shore of Gem Lake, and soon enough you’ll have great views looking over its stunning waters! Gem Lake is actually another reservoir (if you looked carefully earlier when passing Agnew Lake you may have seen the dam) but the views are awesome!
Always be sure to follow the 7 Leave No Trace Principles when in the outdoors!
The mountains immediately surrounding Gem Lake are more of the low, desert-y, variety (similar to the mountains above Agnew Lake), but from the trail well above the water’s edge you can often see the high peaks in the distance!
To The Trailhead:
Once you get to Gem Lake, you may be thinking Agnew Lake and the trailhead beyond is a short walk away. You would be wrong. You’ll be walking along the shores of Gem Lake for close to 2 miles, and throughout those 2 miles you’ll have relentlessly undulating trail to deal with!
The trail looks flat through this section when viewed on a topographic map, but if you zoom way in and look super closely, there are actually a ton of ups and downs. Very rarely is the trail around Gem Lake truly flat. You’ll have a short 100 foot descent followed by a 60 foot climb followed by a 30 foot descent followed by a 40 foot climb. Exhausted yet?
We certainly were! We were approaching mile 15 of the day, the sun was incredibly hot, it was the hottest time of the afternoon, and we were still climbing! It honestly felt like torture to still have to climb at this point in the day, but what is there to do other than keep going?
Eventually you’ll make it all the way around Gem Lake (you will, I promise) and upon arrival at the terminus of the reservoir, you’ll have a great view looking down towards Agnew Lake.
The trail from Gem Lake to Agnew Lake descends sharply along the hillside and actually is a pretty sweet section of trail. It’s a bit rough and rocky, especially to start, and even though I was totally burnt out, I found myself enjoying this bit of hiking!
You’ll arrive at Agnew Lake pretty quickly, and from there it’s just the exposed trail down to Silver Lake! Again, this is a really nice trail that I found myself enjoying! However, the descent from Agnew to Silver Lake is really rocky, and our progress slowed to a crawl! We were sore, and the ankle busting stones along the trail made every step tricky.
Roadtripping to Mammoth? Check out all of our road trip planning tips!
After a final descent that took way longer than we had hoped, we finally arrived back at the trailhead! This is about as tired as I’ve ever been after a hike, and despite bringing close to 4 liters of water, I was definitely dehydrated by the end! It was a brutal day, but it was worth it in the end!
Topdown Lifestyle Rating: 9/10
When you get a hike this long, it can be a little tough to evaluate. For one, over the course of 18 miles you will almost certainly have a couple of miles of forest walking or gravel roads or something that just isn’t that amazing, and that is true for this hike. There were significant sections where I wasn’t enjoying myself at all!
However, you also have to balance that with all of the great, and I especially believe that trails shouldn’t be marked down because you don’t enjoy it due to lack of fitness, not bringing enough water, or other self-inflicted wounds. (We probably didn’t have enough water and were thoroughly beat by the end of this hike!)
This is an amazing hike through some of the best scenery you’ll find anywhere, but for me, it doesn’t pass the true test of a 10/10 hike: will you still be talking about this hike in 10 years?
That may seem like a ridiculously high bar, but I can honestly say I still think about the best hikes I’ve ever done, and those are the benchmarks for me. At this length my go to comparison is Half Dome. Is this hike as memorable as hiking Half Dome? Not for me.
So this is an amazing loop, but it is not quite a 10/10. But seriously, if you can make it, visit Thousand Island Lake!
Pros:
- Tons of amazing alpine lakes
- Incredible views throughout
- Limitless backpacking opportunities
Cons:
- Very busy in spots
- Tons of sun exposure
- Sneaky climbs on the return trip
Alternative Hikes:
When To Hike To Thousand Island Lake:
The Eastern Sierra in general have an excellent climate for hiking, and that holds true for the Mammoth Lakes area. Most days from spring until late fall you will have tons of sunshine, and storms are pretty sporadic, possible, but not daily.
The limiting factor with this hike is snow. You’ll be hiking all the way up over 10,000 feet, so snow can linger well into the summer, and early winter storms could snow this area in early in the year. As a general rule, I’d expect this area to be passable between late June and sometime in October.
In terms of the ideal time to visit, I would probably lean towards earlier in the summer, just after the trails are clear of snow. Most years, that will be in late June or early July. For one, the waterfalls will have more water running through them. The environment will also be a bit more vibrant than later in the year, though fall colors could be very nice.
I think the big one though is that early season fires are much less common than fires in late summer or fall, so you are more likely to have clear, sunny days that are not choked with smoke early in the summer!
Links For Further Reading:
Silver Lake to Thousand Island Lake Loop | Map, Guide – California | AllTrails
Hooves on the Ground: Thousand Island Lake via Rush Creek — dearantler
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