MacKaye was a forester, not a hiker in the modern sense. He envisioned the trail less as a recreation route than as an antidote - a way to reconnect Eastern city dwellers with wild country, with food and shelter that came from the land instead of a factory. Volunteers carried the idea forward through the Depression, clearing brush and blazing the white rectangles that still mark the route today. In 1968, Congress designated it the first National Scenic Trail. The Appalachian Trail Conservancy now coordinates the work of more than 4,000 volunteers who contribute over 185,000 hours each year, keeping shelters in repair, painting blazes, and watching over a corridor of public land that stretches from Georgia to Maine.

Every March, hundreds of would-be thru-hikers start north from Springer Mountain in Georgia, hoping to reach Katahdin before snow closes Baxter State Park in October. About three in twenty make it the whole way. Most stop within the first few hundred miles - feet broken down by humidity, knees worn out by descents, resolve eroded by rain. The trail does not care. In 1955 a 67-year-old grandmother from Ohio named Emma Gatewood became the first woman to solo thru-hike the AT, carrying a homemade sack and wearing Keds sneakers. She did it again in 1957 and once more in 1964. Bill Bryson's 1998 book A Walk in the Woods made the trail famous to a generation who never set foot on it - and recruited a generation that did.

A thru-hike takes roughly five million footsteps. Veterans cover 18 to 25 miles a day; beginners often manage 8 to 10. The Hundred-Mile Wilderness in northern Maine runs without a single paved road across it - one of the last stretches of the route where the corridor truly feels remote. Elsewhere the trail dips into towns where hostels and outfitters have grown up to feed and rest hikers, where general-store owners hold packages of dry pasta and replacement socks at general delivery. Hikers earn trail names from other hikers - never their own - and those names follow them north or south through the seasons. The community is its own kind of thing: looser than a family, tighter than a club, organized around the simple shared fact that everyone is walking the same line.

Because the trail rides the ridgeline, it gets weather the surrounding valleys do not. Storms moving east or west pile up against the Appalachians and dump their rain on the crest. Thunder rolls along the tops of the mountains. In the Smokies and the Whites the route climbs above tree line and exposes hikers to wind that can knock a person down. Mount Washington in New Hampshire has recorded some of the highest surface wind speeds ever measured on Earth. Even in Georgia in April, snow can fall on Springer Mountain. The trail is open year-round, but hiking it outside late spring through early fall is not something to attempt without serious preparation.

Walking it changes people in ways that are hard to articulate from the outside. The days blur together. The body adapts. Conversations narrow to food, weather, water, miles. The trail strips away most of the things that fill ordinary life and leaves behind something simpler. Some hikers describe finishing as anticlimax - the summit of Katahdin appears in the fog, the photograph is taken, and then there is nothing left to walk toward. Others say the trail gave them back a self they had lost. MacKaye understood this when he sketched it more than a century ago. The trail was always meant to be a long line of refuge in a country that was moving too fast.