Cairn Etiquette While Exploring Above Treeline 

By Lily Hartman


As we make our way through the dense forest of lady ferns, tall grass, and spruce and fir trees that surround Caps Ridge Trail, it doesn’t take long for us to pop up above treeline. Even though Mount Jefferson is the third highest summit in New Hampshire, it only takes about 2.6 miles to get there from Caps Ridge Trailhead, which is “the highest elevation trailhead on a public road in the White Mountains,” writes the United States Forest Service (USFS). This means that most of the trail is exposed and, therefore, must be followed by cairns over trail markings for most of the way.

On this trail, you gain elevation quickly—about 2,690 feet in total. The clouds are heavy today. We watch as we make our way into their mist—making it harder to see more than 20 feet in front of us. As we move toward the cone of Mount Jefferson, the only way we know where the trail is, is by following the sturdy cairns that camouflage with the alpine rocks, yet stand out just enough for us to stay on trail.

Building rock structures for guidance is a practice that has been used for centuries around the world, according to Bill Kane, founder and director of The Kane Schools, Wild & Rescue Medicine. In the Northeast, it’s been used since the 1800s to mark trails and guide hikers in the right direction above treeline and in other barren sections, writes the Leave No Trace Center. 

“This was almost a spiritual and smart thing to do,” says Kane. “It gave adventurers confidence that we knew the way—we could go back and forth.”

In the White Mountains, cairns are built by professional trail crews with alpine rocks to protect people and nature, according to the Appalachian Mountain Club (AMC). Cairns are a pile of rocks—usually 3 to 5 feet tall—that look man-made, says Mike Cherim, owner of Redline Guiding. They guide hikers in alpine and subalpine areas safely, while simultaneously preventing footsteps from crushing fragile mountain plants.  

When there’s dense fog or whiteout conditions, especially in the winter, you may not be able to see the next cairn. In these situations, Cherim recommends navigating with a paracord by tying a piece of it to the cairn you’re currently at to stay in contact with it, then to go and find the next one. Once you find it, you can communicate to other hiker(s) at the first cairn by tugging or shaking the paracord with a communication system since you most likely won’t be able to see or hear them. Redline Guiding teaches this in their Wilderness Navigation course above treeline.

“The last thing you want to do is leave a cairn, not find the new one, and not be able to find where you were,” says Cherim. “Now you’re lost.”

Another way to stay on trail—when cairns aren’t visible—is by using a map and compass and orienting your compass to north before leaving the trailhead, which can make all the difference in whiteout conditions, according to Kane. 


Hikers following cairns

Hikers following cairns in low visibility heading up Mount Madison. Photo by Jamal Hicks

Cairns vs Rock Stacking: How to SPOT the Difference

Navigational cairn

• 3–5 feet tall

• 50- to 100-foot distance between each

• Usually placed near ledges or mounds

• Looks like other cairns 

• Wide at the base as they are high

improperly built cairn

A poorly-built cairn, also known as rock-stacking

Unauthorized rock stacking

• Smaller in size

• More artistic 

• May be grouped together

• Often spotted near streams and rivers

• Rocks are often stacked right on top of one another

Navigational Cairns vs. Unauthorized Cairns

Around 2014 or 2015, rock stacking started to become popular as an international art form due to trends on social media, according to Lonely Planet. Cherim says that these rock piles are typically small, artistic, and aren’t navigational cairns. In fact, he says these types of cairns can create a “navigational nightmare” for hikers who believe that they are there as a trail marker.

“There is a tradition in places that if you see a cairn, it’s good luck to put a rock on it,” says Cristin Bailey, trails manager of the USFS Saco Ranger District. “That becomes a problem concerning trail finding and safety, and it’s all over social media.”

When someone places a rock on the top of a cairn, this prevents air and water from getting through it easily and therefore blocks the cairn from drainage. Water can then build up, freeze in cold conditions, and eventually burst—forcing trail crew members to have to rebuild it come spring. 

Unauthorized cairns are often built by streams and rivers, as well as on edges of cliffs, which can take away from the experience of being in nature. Bailey says, “… if we see them, we knock them down [once people leave]. It’s part of our job to maintain the trail in a way that people will use it or not get lost.”

In July, Yosemite National Park rangers told hikers to knock down rock piles when spotted, since they go against leave no trace principles and can disturb ecosystems. In this area, Cherim says that it’s okay to knock down an unauthorized cairn if hikers are certain it’s not a navigational one. Otherwise, “If they don’t know the difference, they shouldn’t be touching them,” he says.

The Nature of Cairns and their Construction

The graphics and text below were paraphrased from the AMC Trail Adopter Handbook—White Mountain Adopt-A-Trail Program.

The handbook was designed as a guide for AMC trail adopters, and provides essential information about how to maintain trails and available resources. The following is just a small sample of the information provided.

Cairns are rock structures used to mark trails in treeless areas. They are an important safety feature above treeline where the trail may not be visible in fog or storms.  They are effective year-round because of their visibility even under snow and ice conditions of winter. They also protect the environment in alpine areas by keeping hikers on the trail. 

On trails that are fairly straight, cairns are typically spaced about 100 to 200 feet apart, and less in areas subject to heavy fog. For trails that are not straight, cairns are placed at turns or bends in the trail to keep hikers on the trail. Cairns are usually placed in conspicuous locations, such as knolls or ledges, and those placed in optimal locations against the skyline can be visible for a mile or more. 


properly-built cairn on Mount Washington

Building cairns is time-consuming and, like much rock work, as much an art as a science. Large, flat rocks are favored in cairn construction, and therefore locating and carrying suitable rocks can take as long as building the cairn. Each layer is sloped slightly to the center so that gravity will stabilize the cairn. The center of cairns are filled with rubble, usually bigger stones as smaller ones can condense together, allowing the cairn to collapse in on itself. Successive layers are built and joints are bridged by additional stones. Each stone typically has at least three points of contact with underlying stones for stability.  

Cairn builders are discouraged from using small stones to fill cracks as shifting produced by wind and frost action will eventually cause these small pieces to come out and the cairn to collapse. Finally, a white rock should be placed on top of the cairn for additional visibility.

Explore trail maintenance opportunities with AMC. Additional information can be found by visiting


Protecting Fragile Ecosystems

Hikers who build rock piles are putting fragile mountain plants at risk by impacting soil and potentially leading other hikers into protected areas. According to Bailey, the White Mountains have the most diverse alpine communities east of the Rockies. There are several species that exist nowhere else in the world besides above-treeline areas in the White Mountains, such as the dwarf cinquefoil and White Mountain Fritillary butterfly, which is why it’s considered a special place to protect in the forest.

“By design, trails are supposed to concentrate the impacts of recreation,” says Bailey. Hikers should only step on the treadway in rocky terrain, which is why trail crews are advised to place cairns in a way that keeps foot traffic away from fragile alpine gardens.

What it Takes to Build a Cairn

USFS partner trail crews are responsible for maintaining existing structures in the White Mountains, including cairns, according to Bailey—whether that’s a staff crew, weekend or week-long volunteer group, or team of an adopted trail program. Trail crew members are provided drawings by the USFS and AMC that instruct them on how to build a cairn.

Building cairns is different than other kinds of trail work. There are different safety precautions to follow, but it’s a much more rewarding experience. Large, heavy rocks can be difficult to carry, and there’s a certain technique to doing so. When putting rock on rock, it’s very easy to pinch a finger, Bailey says.

Volunteers needed

“We need more volunteers and people just being aware and supporting trails however they can—everybody’s got time, talent, or treasure.” – Cristin Bailey, trails manager of the United States Forest Service Saco Ranger Station.

The USFS provides training, year-round opportunities, and the ability set your own schedule for stewardship
More info:

Adopt-a-Trail opportunities: www.naturegroupie org/services/adopt-trail-opportunities 

AMC: Explore trail maintenance opportunities with AMC. Every year, AMC staff works alongside thousands of volunteers to maintain and build trails. By joining a trail crew, you can combine your passions of being outdoors and contributing to the protection of the environment. More info:

After hours of hiking to the subalpine or alpine areas that need a new or updated cairn, trail maintainers get to work. To begin, the crew selects rocks that aren’t holding back soil in order to keep those areas protected. For each tier, and especially the base layer, crew members use large, flat rocks and angle them towards the center to increase gravity. Each stone needs three points of contact to stabilize the cairn and eliminate wiggle. Small rocks are also used to backfill the cairn to further strengthen it. They’re built 50 to 100 feet apart on easy-to-spot ledges or mounds and a light-colored rock is also often placed on top for greater visibility.

“The cairns are established—they need to be structurally sound, but you also need to have a rock available, which is not always the case—ironically,” says Bailey. “Just for the summit cone of Mount Washington, we had to fly rock to use.”

Respect Nature

From a navigational cairn made by a professional trail crew to someone creating art for mindfulness, the tradition of building cairns doesn’t seem to be going anywhere. According to Cherim, knowing the difference between each motive is important when spending time in nature.

“Have fun, play by the river—that’s fantastic,” says Bailey. “We want you to do that, but please  knock down the cairn you built before you go.”

CAIRNS & Leave No Trace

leave no trace

We are fortunate to have diverse outdoor recreation opportunities, many of which are in sensitive environments such as areas near or above treeline. Cairns are prominent features in many of these alpine areas. Special care should be taken to both enjoy these areas responsibly and to ensure that cairns are left as they are found. 

Cairns are intentionally constructed stacks of rocks that mark trails and guide hikers in the mountains above treeline, and in other barren areas. These route markers have been in use in the Northeastern U.S. since the 1800s. Cairns are very important guides for hikers during periods of low visibility (dense fog and whiteout) and in winter when snow covers the trail.    

By adhering to the following guidelines, you can minimize impact on cairns, and ensure that cairns continue to serve as a critical route-finding tool for trail users and resource protection tool for the alpine landscape. 

• Do not build unauthorized cairns. When visitors create unauthorized routes or cairns, they often greatly expand trampling impacts and misdirect visitors from established routes to more fragile or dangerous areas. This is especially important in the winter when trails are hidden by snow. Thus, visitor-created or “bootleg” cairns can be very misleading to hikers and should not be built.

• Do not tamper with cairns. Authorized cairns are designed and built for specific purposes. Tampering with or altering cairns minimizes their route marking effectiveness. Leave all cairns as they are found.

• Do not add stones to existing cairns. Cairns are designed to be free draining. Adding stones to cairns chinks the crevices, allowing snow to accumulate. Snow turns to ice, and the subsequent freeze/thaw cycle can reduce the cairn to a rock pile. 

• Do not move rocks. Extracting and moving rocks make mountain soils more prone to erosion in an environment where new soil creation requires thousands of years. It also disturbs adjacent fragile alpine vegetation.

• Stay on trails. Protect fragile mountain vegetation by following cairns or paint blazes in order to stay on designated trails.

To learn more about Leave No Trace practices for the Northeast mountains, please visit or call 1.800.332.4100.