Why is Devils Postpile a must-see geological wonder?

Rare columnar jointing formed when basaltic lava cooled slowly, creating uniform vertical cracks. The hexagonal pillars, some reaching 60 feet, were later exposed by glacial action. The clean vertical wall polished by ice makes it a textbook example of lava flow geometry.

Devils Postpile National Monument — RV Travel Guide

By PickRV·Cited primary sources·Updated June 26, 2026

Devils Postpile National Monument showcases one of the world's finest examples of columnar basalt—a honeycomb-like wall of hexagonal pillars rising up to 60 feet. Formed by cooling lava roughly 100,000 years ago, the monument sits in the heart of the Sierra Nevada near Mammoth Lakes, California. A short trail leads to the base of the columns, while nearby Rainbow Falls plunges 101 feet over a volcanic cliff. Managed by the National Park Service, this compact monument blends geological wonder with alpine scenery, making it an essential stop on the eastern Sierra tour.

Best season — Late June through early October, when the access road and shuttle operate for full sightseeing. Winter snow closes the road, limiting access to over‑snow travel.

At a glance

The facts worth checking before you roll out

Conservative, source-minded facts for planning your visit — always worth confirming against current conditions before you travel.

Managing agency

National Park Service (U.S. Department of the Interior)

State

California (Sierra Nevada, near Mammoth Lakes)

Established

1911, by presidential proclamation

Defining characteristic

One of the world's finest examples of columnar basalt; also protects the 101-foot Rainbow Falls

On the ground

Devils Postpile National Monument preserves a remarkable geological feature—columnar basalt. This formation, created by slow cooling lava approximately 100,000 years ago, presents as an unusual wall of hexagonal pillars reaching up to 60 feet high. The National Park Service manages this site in the Sierra Nevada near Mammoth Lakes, California, safeguarding it for future observation and study.

RV travelers visiting Devils Postpile typically access the monument via shuttle during the open season. Activities center around viewing the basalt columns and a visit to Rainbow Falls, which plunges 101 feet over volcanic cliffs. The site draws those interested in geology, photography, and short hiking trails near the Middle Fork San Joaquin River.

The best time for RV travel to Devils Postpile is late June through early October. During these months, the access road and shuttle system are fully operational, providing convenient access. Winter conditions bring significant snowfall, closing the road and limiting monument access solely to over-snow travel options.

Consider establishing a basecamp in the general vicinity of Mammoth Lakes for exploring Devils Postpile and other eastern Sierra attractions. This allows flexible day trips utilizing the park’s shuttle system when available. The area offers diverse scenery with opportunities to combine geological sightseeing with alpine landscapes.

Official sources

National Park Service — Devils Postpile National Monument National Park Service

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