Rock Cairns in National Parks: What Those Stacks Mean, and Why You Shouldn't Build Them

A rock cairn above the sea. Image from the National Park Service's page

Hiking in a national park, you may come across stacks of rocks. These are cairns, and in many parks they mark hiking routes. But every park has its own rules about them, so check the park's website for trail information before you go.

Parks that use cairns

At parks such as El Malpais, Hawaiʻi Volcanoes and Acadia, staff carefully maintain cairns to keep hikers on the right path — and they come in different shapes:

Cairns mark an ancient path through the lava on the Zuni-Acoma Trail, El Malpais National Monument. NPS

Unsure whether to follow a cairn? Ask a returning hiker or a ranger.

Parks that don't

Some parks, like Capitol Reef National Park in Utah, don't build or maintain cairns and warn visitors not to rely on them. Any cairns there are ornamental — and they can mislead hikers who think they're meant to follow them.

A rock cairn at Canyonlands National Park. NPS / Neal Herbert

One rule everywhere

If you find a cairn, leave it alone. Don't knock it down, and don't add to it. Following Leave No Trace guidelines keeps the trail findable and the land intact:

• Don't tamper with cairns. Moving an official cairn — or building an unofficial one — can disorient or lose later hikers.
• Don't build your own. Moving rocks disturbs the soil, invites erosion, and damages fragile plants and small ecosystems.
• Don't add to existing cairns. Official cairns are carefully designed, and extra rocks can make them collapse.

A shareable tip card about cairns. Image from the National Park Service's page

Pass it on

Nobody can know everything. If you see someone stacking rocks, share what you've learned — kindly.

Sources

Based on "I Didn't Know That!: Rock Cairns," National Park Service; a work of the United States government in the public domain.