Near Mammoth Lakes, a lava wall rose from the earth, and you can walk right up to it

It’s hiding near Mammoth Lakes

Devils Postpile National Monument sits in California’s eastern Sierra Nevada, just outside the town of Mammoth Lakes, and it protects one of the finest walls of columnar basalt on the planet.

The columns rise up to 60 feet, packed tight like enormous stone posts. The U.S. Geological Survey backs that claim.

Across roughly 800 acres, you also get Rainbow Falls, pine forests and real High Sierra wilderness. The geology alone is worth the drive, but the falls and the trails around them make it something else entirely.

Lava pooled 400 feet deep and cracked into columns

Between 80,000 and 100,000 years ago, basaltic lava poured into this valley and hit a natural dam. The lava pooled up to 400 feet deep, then cooled slowly and evenly.

As it contracted, it cracked into columns, and the uniform mineral makeup of the lava gave most of them a clean hexagonal shape.

About 65,000 years later, a glacier scraped through the valley, stripped away the loose rock and exposed the columns underneath. What fire built, ice revealed.

John Muir fought to save it from dynamite

The monument was once part of Yosemite National Park, but a gold discovery near Mammoth Lakes in the early 1900s pushed the government to redraw the boundary. That left the Postpile unprotected.

When a proposal came to blast the formation for a hydroelectric dam, John Muir and other influential Californians lobbied hard to stop it. They won.

President William Howard Taft made it a national monument in 1911, and the columns have stood untouched ever since.

A half-mile walk puts you at the base

You don’t need to be a serious hiker to reach the Postpile.

A mostly flat trail of about half a mile leads from the ranger station straight to the base of the formation. From there, you look up at columns stacked tight together, many perfectly straight and uniform.

Most average about two feet across, though the largest ones stretch to three and a half feet.

A survey of 400 columns found that while most have six sides, some have four, five or seven, depending on how the lava cooled.

The top looks like a tiled stone floor

A steeper trail climbs from the base to the top of the formation, and the view changes completely.

From above, the column tops look like a geometric tile floor, hexagonal shapes polished smooth and fitted tightly together. Glaciers did that polishing thousands of years ago, and you can still see the sheen today.

Look closely and you’ll spot glacial striations, scratches cut into the rock that mark the direction the ice traveled. It’s one of the most photographed spots in the monument for good reason.

A 101-foot waterfall throws rainbows at midday

About two and a half miles from the ranger station, the Middle Fork of the San Joaquin River drops 101 feet over a volcanic cliff.

Rainbow Falls is the tallest waterfall on this stretch of river, and on sunny days around midday, rainbows appear in the mist.

You can take it in from overlooks above, or hike down a set of stairs to the base for a closer look.

The surrounding cliffs are made of rhyodacite, a different volcanic rock formed by a separate lava flow roughly 75,000 years ago.

Eight miles of trails through pine and wildflower

The monument holds about eight miles of trails. The Devils Postpile Loop covers 1.2 miles and takes you around and over the formation.

If you want the waterfall too, the trail from the ranger station to Rainbow Falls and back runs about five miles with moderate elevation change. You can combine both in half a day.

Along the way, you’ll walk through pine forests, follow the San Joaquin River and pass through areas still recovering from a 1992 wildfire, where wildflowers and grasses have taken over.

Two legendary trails merge into one path here

The John Muir Trail and the Pacific Crest Trail both pass through the monument, and for a stretch inside its borders, the two merge into a single path.

The John Muir Trail runs roughly 211 miles from Yosemite Valley to Mount Whitney, the highest peak in the lower 48 states. The Pacific Crest Trail stretches about 2,650 miles from Mexico to Canada.

Day hikers and backpackers use the monument as a launching point for trips into the surrounding Ansel Adams Wilderness.

Minaret Falls hits hardest in early summer

Just outside the monument boundary, Minaret Falls is an easy three-mile round trip from the ranger station.

The trail follows a portion of the Pacific Crest Trail and crosses a bridge over the San Joaquin River before reaching the cascade, which runs strongest in early summer when snowmelt peaks.

Nearby, Sotcher Lake is a small spring-fed lake with a 1.5-mile loop trail that draws anglers and picnickers.

If you want to push deeper, alpine destinations like Minaret Lake and Fern Lake wait in the Ansel Adams Wilderness.

Indian paintbrush and shooting stars fill the meadows

From mid-June through mid-July, the valley floor lights up with wildflowers.

You’ll find Indian paintbrush, red columbine, monkey flower, meadow larkspur and Sierra shooting star scattered through the grass.

The Agnew Meadows wildflower trail covers just 0.6 miles and packs in some of the best color and variety.

Soda Springs Meadow, near the ranger station, sits along the winding San Joaquin River with pine forests on all sides. Show up at dawn or dusk and you might catch mule deer grazing at the edges.

Black bears, pine martens and wild trout in the river

More than 100 species of birds live in the monument, including Steller’s jays, dark-eyed juncos, white-crowned sparrows and bluebirds.

Dawn and dusk give you the best chance at spotting black bears, pine martens, mule deer and coyotes.

The Middle Fork of the San Joaquin River carries a Wild Trout designation, with rainbow, brown and brook trout in the water.

Fly fishing is popular along the meadow stretches, and you’ll need a valid California fishing license to cast a line.

230,000 acres of wilderness wrap around it

Nearly all of the monument lies within the Ansel Adams Wilderness, which covers more than 230,000 acres of the Sierra Nevada. Alpine lakes, granite peaks and dense forests stretch in every direction.

The jagged Minarets of the Ritter Range rise into view from many points in and around the monument.

The monument itself sits between roughly 7,200 and 8,200 feet, and backpackers heading deeper into the wilderness need permits from the Inyo National Forest before setting out.

800 acres packed tight next to Mammoth Lakes

The town of Mammoth Lakes is just a short drive away, sitting along U.S. Route 395 in California’s Eastern Sierra. Yosemite National Park is a neighbor too, accessible through Tioga Pass during the summer months.

For a monument that covers only about 800 acres, Devils Postpile fits a lot into a small space: rare volcanic geology, a 101-foot waterfall, two of the country’s most famous long-distance trails and alpine wilderness on every side.

Compared to the national parks nearby, it’s tiny. But it doesn’t feel that way once you’re in it.

Explore Devils Postpile National Monument in California

If you want to see those basalt columns and Rainbow Falls for yourself, Devils Postpile National Monument is open seasonally, generally from mid-June through mid-October, depending on weather.

During peak season, a mandatory shuttle bus runs from the Mammoth Mountain Main Lodge to the trailheads in the valley, so plan around the shuttle schedule.

Road and access conditions can shift, so check the official website before you go. Admission runs $15 per adult, and kids 15 and under get in free.

This article was created with AI assistance and human editing.

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