Devils Postpile National Monument: What to See & How to Visit

Roughly 80,000 to 100,000 years ago, a massive lava flow erupted from a vent above the Middle Fork of the San Joaquin River and pooled into a deep lava lake, filling the valley to a depth of 400 feet. As the lava slowly cooled, it contracted and cracked into an orderly geometric pattern—most of the resulting columns are hexagonal, though you'll find pentagons and heptagons among them, a natural consequence of the cooling process.

Then came the ice. During the last Ice Age, glaciers overrode the fractured basalt and quarried away one side of the postpile, polishing the column tops to a mirror-smooth finish and exposing the sheer 60-foot wall visible today. The honeycomb pattern visible from above, best seen from the summit of the formation, is one of the most photographed geological surfaces in the Sierra Nevada.

Devils Postpile is part of the broader Long Valley volcanic landscape that makes the Mammoth Lakes region one of the most geologically active areas in North America. The same volcanic forces that created Mammoth Mountain, Hot Creek, and the Inyo Craters also shaped this valley.

Hiking at Devils Postpile

Devils Postpile has 8 miles of trails ranging from easy strolls to longer backcountry routes into the Ansel Adams Wilderness:

• Postpile Base Trail: 1 mile round-trip, easy. Walk the San Joaquin River to the base of the columns.
• Postpile Summit Loop: Adds a short uphill climb to the polished column tops. Strongly recommended.
• Rainbow Falls Trail: 2.5 miles from the ranger station (or 1.5 miles from the Rainbow Falls shuttle stop), easy to moderate. The most popular hike in the monument.
• John Muir / Pacific Crest Trail: Passes through the monument for those looking to venture deeper into the wilderness.

Fishing the San Joaquin River

The San Joaquin River through Reds Meadow is a designated Wild Trout River, offering excellent fly fishing for rainbow and brown trout. Prime spots line the banks near the shuttle parking area and farther downstream past Soda Springs Meadow. Pick up gear and a California fishing license from a Mammoth Lakes outfitter before you go.

Wildlife Watching

Devils Postpile and Reds Meadow Valley are home to over 100 bird species and a healthy population of Sierra Nevada mammals, including black bears, mule deer, pine martens, and coyotes. Dawn and dusk are the best times for wildlife encounters—give all animals plenty of space and never approach or feed them.

Devils Postpile is one stop on one of the most remarkable geological road trips in the American West. The same volcanic and glacial forces that shaped this valley created an entire landscape of wonders within a short drive.

Rainbow Falls: The Falls are a 1.7-mile hike from the Devils Postpile ranger station or a short walk from the dedicated shuttle stop. Arrive around midday when the sun hits the mist and produces the rainbows that give the falls their name.

The Minarets & Minaret Vista: The jagged spires visible above the valley are the Minarets—ancient metamorphic and volcanic rock that predates the Sierra Nevada granite batholith by hundreds of millions of years. They're among the oldest exposed rocks in the range. The best unobstructed view is from Minaret Vista, just above the monument on the road in from Mammoth Mountain, and it costs nothing but a short stop. For those wanting to go deeper, the Minaret Lake Trail departs from the Devils Postpile trailhead and climbs into the Ansel Adams Wilderness beneath the peaks.

Mammoth Mountain: The broad volcanic dome rising above the town is a 100,000-year-old lava complex—geologically young by Sierra standards and part of the same volcanic system that produced this valley. Ride the gondola to 11,053 feet and visit the Eleven53 Interpretive Center for an overview of the region's entire volcanic history, from the Long Valley Caldera eruption 760,000 years ago to the features you explored today.

Hot Creek Geological Site: Eight miles southeast of downtown, Hot Creek is where the region's volcanic energy reaches the surface most dramatically—boiling geothermal springs bubble up through a river gorge, staining the rock in layers of minerals and sending steam across the water. The same magma system heating Hot Creek is connected to the Long Valley Caldera that underlies this entire landscape. An easy paved trail descends into the gorge from the parking area.

Inyo Craters: Six hundred years ago, groundwater hit partially molten rock deep below the surface, and the result was a cataclysmic steam explosion that shot rock miles into the air and left a few deep crater scars in the forest north of town. The Inyo Craters Trail reaches the crater rim in just under a mile from the parking area, with views stretching from the San Joaquin Ridge to the White Mountains.