The Appalachian Trail is now such a fixture of the New England landscape that it’s easy to forget how improbable it once seemed. When Connecticut-born Benton MacKaye first sketched out a proposal for a 2,000-mile footpath along the spine of the Appalachian mountains in 1921, nobody had ever built such a thing. Why would they? The trail MacKaye envisioned would connect nowhere in particular, serve no commercial purpose, and require a massive effort in some of the most inaccessible reaches of the Eastern wilderness.

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Hikers pass through Sargent’s Purchase in New Hampshire.

The success of the trail, which officially opened 75 years ago today, is a testament to how deeply MacKaye’s call to set aside quiet escapes in a busy world resonated then and continues to resonate now. With the help of thousands of volunteers, the trail’s white blazes extend through every New England state except Rhode Island, culminating in the final rocky ascent up Mount Katahdin. In all, about 3 million people hike over some portion of the Maine-to-Georgia trail every year, and its popularity has inspired the creation of long-distance trails in other parts of the nation and abroad.

Unlike a highway, which imposes itself on the land, the exact route of the Appalachian Trail is in constant negotiation with the forest, changing with each winter storm and spring flood. Only about 1 percent of the original footpath remains. But the mission MacKaye envisioned for the trail — as “a sanctuary and a refuge from the scramble of every-day worldly commercial life” — remains precisely the same.