In 1850 old-growth forests composed 51 percent of Minnesota's timberland. Forests in the northeastern triangle of the state were so thick and looming in some areas that they blocked the sun. My great-grandfather Peter Pearson, fleeing the effects of famine in Sweden, was among the immigrants who arrived in the region in the late 1800s to carve a new life out of cutting trees. Settling in the boom town of Tower, he sawed Norway and white pine for lumber, spruce and balsam for pulpwood, and birch for railroad ties. By 1994 old-growth forests had dwindled to 4 percent of Minnesota timberland.

A tree is a tree is a tree, one might think, especially in a state that is blessed with billions of them. But I have a particular fascination with old, especially old-growth, trees. Perhaps that's because I'm sensitive to my great-grandfather's role in their demise, or maybe it's the result of having spent hours gazing up at the at the long needles growing from gnarled branches on the 100-foot-tall Norway pines holding my hammock on the shoreline at our family's longtime cabin on Lake Vermilion.

In her quietly mesmerizing book Nature's Temples: The Complex World of Old-Growth Forests, scientist Joan Maloof defines an old-growth forest as one that has "escaped destruction for a long enough period of time to allow natural and biological ecosystem functions to be the dominant influence." From a conservation perspective, old-growth forests often hold a wider range of life and are, tree for tree, generally taller than managed forests. They also harbor history, beauty, and mystery. The oldest known tree in the world is a Great Basin bristlecone pine in California that is pushing five millennia. By comparison, Minnesota's ancient ones date back four centuries or more. Many can be found in 10 easily reached protected areas open to the public across the state, according to the Department of Natural Resources website.

But other unsung stands of old-growth forest still exist—if you know where to look. I was thrilled, several years ago, when my friend Marcus Hess invited me to see a hidden grove of old-growth cedar on an island in a large bay on the west end of Lake Vermilion. On a windy day we paddled our canoe a half-mile straight into a headwind. The waves were white-capped, wet, and invigorating.

When we reached the island, we beached the boat in an isolated cove, then started bushwhacking through dense scrub in the direction of the trees. It was slow going without a trail. After half an hour, the underbrush cleared and the mellow, soothing aroma of cedar led us to what looked like an outdoor chapel. Light filtered through the dense canopy, and, with no underbrush, the forest floor appeared to be swept clean. Despite the wind on the lake, the trees held the silence. I sat in wonder on a downed log, guessing at why they had escaped the fate of saws and disease, grateful to my friend for sharing his secret.

A year later Marcus died suddenly of cancer. He was the only person I knew who knew of the trees' existence. Because my memory of that day now feels so fleeting and dreamlike, I recently confirmed with Terry Bergstrom, a DNR forestry technician based in Cook, that the cedars are indeed old-growth. He told me they sit on 30 acres of public land, a plot that is "unusual for how parklike and pure the cedar is."

I'm tempted to try to find the cedars again, to share their beauty with others, as Marcus so generously shared them with me. But I've decided not to act upon that impulse. It's probably best to just let them be.

Stephanie Pearson writes for Outside and other publications. Explore old-growth forests in Minnesota.