But at each stop along the way, many clues emerged, until a rather obvious answer presented itself to the question of when and where he was happiest.

You start in Sun Valley. The Nature Conservancy protects the heart of Silver Creek, one of the world’s great fly fishing waters, as well as the splendid residence where Hemingway took his last breath. You can see what drew him here. “Best of all he loved the fall,” Hemingway wrote, in a eulogy to another resident, though he could have been describing his own feelings, “the leaves yellow on the cottonwoods, leaves floating on the trout streams, and above the hills the high blue windless skies.”

In his last years, Hemingway could no longer find that joy in nature and simple things. He was racked by depression, bipolar mood disorders and alcoholism, and had recently been treated with electroconvulsive shock therapy. He had delusions that could be described as psychotic. He was struggling with a novel and the Paris memoir; on many days, the words would not come. The question arises, as with Vincent Van Gogh or any other great artist cursed with mental illness: What would Hemingway on meds be like? Would he even be Hemingway?

In Key West, a driving distance of nearly 3,000 miles from here, you hear all the tales of debauchery and good political fights. With his second wife, Pauline, Hemingway lived during the 1930s in a Spanish Colonial built of native rock in the Old Town. He drank to excess, brawled with friends and lovers, but managed to be at his typewriter in a second-floor studio at dawn. He labored to put out 800 or so words a day — a lesson for all writers who wait for tardy muses. There he wrote, “The Snows of Kilimanjaro,” and “To Have and Have Not” and “The Short Happy Life of Francis Macomber.”

From his letters, and accounts of the time, he was too restless, emotionally, to be happy in Key West. Fame had reshaped him; he needed conflict. When you stare at the walls and feel the claustrophobia of his work room, when you imagine him reaching for a few good words, you understand why he said, after winning the Nobel Prize for literature, that “Writing, at its best, is a lonely life.”