“I do think I knew somewhere in the back of my head that Walden was near Concord,” Ms. Devers said. But like many wayfarers in a world increasingly reliant on GPS devices, “I just didn’t really process the directions.”

On its support Web site, Google says it considers the user’s location, in part, to determine its mapping search results — but a search from Cambridge, Mass., for example, returns Lynn’s reservoir, even though the Concord pond is closer in both miles and travel time. Although the simple phrase “Walden Pond” tends to pull up the Lynn reservoir, additional autocomplete options do show the site in Concord. (MapQuest and Microsoft’s search engine, Bing, first pull up the Concord Walden Pond.)

“It happens all the time,” said Dan Small, the ranger for Lynn Woods, where the reservoir is.

Dick Katin, a ranger at the neighboring golf course, has found himself zooming over the green in his cart to collect misdirected visitors who wander through the fairway, seeking Walden. “Which is very dangerous,” he said. “They don’t pay attention when they’re walking through here. They think they’re on a trail hiking or whatever.”

The Lynn Walden Pond itself is a scenic place, although the few empty beer cans that dot the surrounding woods and the lack of cabin often clue people in to the fact that something might be amiss. “We finally get there, and we’re like, is this it?” said Jeremy Corn, a restaurant beverage director who used his iPhone to navigate a trip to Walden Pond during his honeymoon road trip, inspired by his new wife’s love of Thoreau. When the two took a closer look at the map, they realized where they were — or rather, weren’t.