Devils Postpile National Monument

Devils Postpile protects a wall of basalt columns up to 60 feet (18 m) high and the 101-foot (31 m) Rainbow Falls, in a valley of the Middle Fork San Joaquin River near Mammoth Lakes. It is a short walk for families, and also a busy crossing point for the John Muir and Pacific Crest trails.

Fast facts

• Established: 1911
• Size: about 800 acres (3.2 km²)
• Signature features: columnar basalt up to 60 feet (18 m) tall, and Rainbow Falls, 101 feet (31 m)
• Elevation: about 7,560 feet (2,300 m)
• Gateway: Mammoth Lakes, California
• Managed by: the National Park Service, surrounded by Inyo National Forest

The landscape

The Postpile formed when a lava flow cooled slowly and cracked into long, mostly six-sided columns, later polished by glaciers; the top of the formation looks like a tiled floor. Below it, the Middle Fork San Joaquin runs through a forested valley to Rainbow Falls, where rainbows form in the spray on sunny days. Much of the valley burned in the 1992 Rainbow Fire and is regrowing.

Best time to go

The monument is open in summer and early fall, usually from mid-June until snow closes the road by late October. July and August are busiest, with afternoon thunderstorms possible; September is quieter and cooler, with frosty nights.

Getting there and around

From US 395, take SR 203 to Mammoth Lakes and continue past Minaret Vista, then down a steep, partly single-lane road into the valley. While the shuttle runs, from about mid-June to just after Labor Day, most visitors must park at Mammoth Mountain and ride the shuttle bus in. The ranger station is the starting point for the main trails.

Things to do

From the ranger station it is about 0.5 miles (0.8 km) to the base of the Postpile, and a short, steeper loop climbs to its polished top. Continue to Rainbow Falls for a rolling hike of about 5 miles (8 km) round trip; stairs lead to the bottom of the falls.

The John Muir and Pacific Crest trails pass through the monument on their way between Yosemite and the High Sierra, and the Ansel Adams Wilderness surrounds it. Backpackers use the valley and nearby Reds Meadow as a start, finish or resupply point for multi-day trips.

Staying safe

At 7,500 feet (2,300 m), altitude can tire visitors from sea level, and afternoon thunderstorms bring lightning to exposed spots. Stay off the unstable talus (loose broken rock) at the foot of the Postpile. The river is cold and fast, especially near Rainbow Falls. Black bears are active, so store food properly.

Know before you go

The shuttle is mandatory for most visitors while it runs, with exceptions such as campers and visitors with disabilities. Overnight trips into the surrounding wilderness need a wilderness permit from Inyo National Forest. This page is a general overview, not a live conditions report, so confirm opening dates and shuttle details with the National Park Service before you go.

Coordinates

37.6154, -119.0877

Magnetic declination

12.2° E (2026)

Set this declination on your compass, then align it to the map's north lines; it is the angle between true north and magnetic north, refreshed each year.

How declination works, and how to navigate with a map and compass

Best seasons

Summer, Early fall

Difficulty

Easy to moderate (strenuous on the long-distance trails beyond)

Access / trailheads

SR 203 from US 395 through Mammoth Lakes, then a steep, partly single-lane road. Seasonal shuttle from Mammoth Mountain.

Water

Treat river and creek water; drinking water at the ranger station area in season.

Cell / satellite coverage

Little to none in the valley.

Nearest ranger / SAR / emergency

Emergencies: 911. Devils Postpile ranger station: 760-934-2289.

Permits & regulations

Mandatory shuttle for most visitors in the main season (fee). Wilderness permit from Inyo National Forest for overnight trips beyond the monument.

Leave No Trace

Stay off the talus and the Postpile’s edges, store food in bear boxes, and pack out all waste.