The best way to reach the garden of Eden, I found, was to fly into Kansas City, Mo., rent a car and drive north on Interstate 35 for two hours, exiting at a town named Cameron and following the signs to Adam-ondi-Ahman. The place was marked on my atlas merely as a "Mormon shrine," but having grown up as a Mormon, I knew better. According to Joseph Smith, the farm-boy prophet who at 14 felt his first heavenly inklings and by 30 had attracted thousands of followers, this was where God created humankind and where Christ would return to rule the earth.

I parked in a lot beside two other cars, both of which had Utah plates, and followed a path to a posted overlook. I had been here before, as a devout 14-year-old on a church-led bus tour. Now, a more skeptical adult, I wanted to follow the Mormon trail again, traveling (in the order of settlement) from Missouri, Joseph Smith's abortive Zion, back east to Nauvoo, Ill., the first true Mormon city, then west along the route of exile to Salt Lake City, Utah. Preserving and highlighting the past is a Mormon priority--witness the re-enactment of the wagon train. Leaders of the church seem to understand that its vivid history, as much as its sometimes cloudy theology, is what attracts the potential convert.

Standing beside a clean-cut young couple dressed rather formally for the summer weather, I looked out over Adam's home, a broad green valley that is currently planted in corn. Smith planned a town here that never took hold, just one among several Mormon promised lands, from Kirtland, Ohio, to Independence, Mo., that he and his flock were violently driven from. The public did not like Mormons in those days (segments of it still don't) and charged them with a host of crimes ranging from fraternizing with native "savages" to advocating the abolition of slavery. Smith's early church was a radical institution. It preached communitarian economics, the brotherhood of man and polygamy. But perhaps Smith's deepest break from orthodoxy had to do with geography, not theology: he taught that the New Jerusalem was here, smack dab in the middle of America.

I drove east out of Eden across the Mississippi, reflecting that perhaps Smith's prophecies were not so wacky after all. Even Mark Twain (a notorious Mormon mocker who famously dissed the Book of Mormon as "chloroform in print") set his own idyllic fables along the riverway. Indeed, if God had planted Eden in America, he could not have found better soil or growing weather. Even the air smells fertile in northern Missouri--humid, rich and fertile--almost malted.

In Nauvoo I stopped at the church-run visitors center, up the hill from the restored historic district. The place had changed since I had seen it as a kid. Installed below a towering statue of a decidedly muscular Christ were several video monitors equipped with touch screens. Each screen had a menu of philosophical questions. I selected "What is the purpose of life?" although I was tempted to cut to the chase by touching "Is there life after death?" Instantly a robotic male voice answered, "To see if we will follow the plan of our Heavenly Father, each of us is given two great gifts. One is time, the other freedom of choice...Every day, every hour, every minute of our span of mortal years must sometime be accounted for." The screen showed a high school boy inside his car, a lurid, seductive neon sign reflected in its windshield. The pensive young man looked as though he had suddenly realized he had been wasting precious mortal minutes and had better drive home while there was still time.

I spent another half an hour at the screen, taking advantage of its forthright answers to a veritable maze of cosmic quandaries. As a teenager I had appreciated such certainties; as an adult I was tempted to make fun of them. My secular college professors had insisted that truth is always complicated, relative, but I still felt the tug of religious absolutism. Watching a woman in a wheelchair beside me earnestly punching up answers on her screen, I concluded I was not alone.

I toured what was left of old Nauvoo and learned that Smith had run his growing church from an office above his family's general store. I liked this detail. It brought the man alive for me. Unlike Brigham Young, the stern puritan who succeeded him, Smith was an improviser, a boyish mystic, brimming with charismatic, homegrown visions. In the fields beyond his store, he liked to dress up as a general and drill his personal army, the Nauvoo Legion. In 1844, the year he was murdered, he announced a quixotic candidacy for the U.S. presidency. All in all, it was as if Huck Finn had founded a major religion.

The frontier jail where Smith was killed lies southeast of Nauvoo, in Carthage, Ill. I arrived in the middle of a guided tour: 30 or 40 Mormon teens sat on the floor of a second-story room and listened to a husky, white-haired elder narrate the tragedy of Smith's last hours. The elder, using a walking stick to imitate the rifles of the mob, enacted the death scene with stagey gusto, but when the bloody climax came--Smith's disastrous fall from the building--he grew somber. "I personally think that when Joseph fell out that window, the Savior was right there to catch him." There were tears in his eyes now and more tears on the cheeks of the girl with corn-silk blond hair sitting beside him.

The elder went on to point out two bullet holes in a nearby door, which led to several questions from the kids about the circumstances of the assassination. Did Joseph speak any last words? Wasn't there once a bloodstain on the floor? These kids had seen too many action movies, I sensed, but I could not fault them for their curiosity. Like early Christians eager to handle pieces of the Cross, the kids desired a physical connection with this obscure Midwestern passion play, which was not unlike a 19th century Waco. I felt the same curiosity at their age--intrigued by an American faith that served up not only abstract precepts but also the chance to walk in the footsteps of its heroes.

After Smith's death and Young's rise to power, those footsteps led due west. Mormons like to compare themselves to Jews; they too had a strenuous exodus: across the Mississippi, into Iowa, through Nebraska and Wyoming, into Utah. For the past two years, a few hundred hardy souls have been retracing this journey on horseback and on foot. Many of the pilgrims are blood descendants of the pioneers, and although their re-creation of the procession includes a few dozen motorized support vehicles, the trek is not for the tenderfoot.

I joined up with the march in western Wyoming, near the ghost town of Piedmont. The wind blew gales of dust into people's faces. Some children were limping. The sun was high and hot. At the head of the party were scores of clattering wagons; to the rear, a long line of pedestrians pulling handcarts. Between the groups, a solitary woman, dressed in a bonnet and a long print dress, strode briskly along with her eyes on her tennis shoes.

Karen Hill had trudged almost a thousand miles since spring and had a hundred more to go. The wife of the trek's organizer, Brian Hill, Karen converted to Mormonism when she was 25. "Everyone has a different reason to be here," she said. Karen's was to support her husband. "What I didn't expect," she said, "was the exhaustion, physical and emotional. I think it was the same for the first saints." She recalled a song she had written miles back: "There are angels among us, there are angels about ...The veil is getting thinner now."

I dropped back a mile and joined the handcart company. Gordon Beharrell, an elderly Englishman, was carrying a fluttering Union Jack in tribute to his 19th century countrymen who had converted to Mormonism by the thousands and walked this route before him. "I intended to re-enact their adventure, but for me this hasn't been a re-enactment. I've experienced real hardship and real pain." Beharrell told an inspiring story then. Before setting out, he was found to have colon cancer and underwent major surgery. Then, as he neared Scott's Bluff, Neb., he fell ill from complications and was hospitalized again. "When I was released, I could barely walk five yards. I had to be loaded on a cart and pulled. Then two elders gave me a healing blessing. The next Wednesday I managed to walk two miles, then six the next day, then 11 the next. Soon I was making 25 miles a day, and I've been going steady ever since. I attribute all this to a certain British grit, but mostly to the power of that blessing."

There were other sojourners with tales to tell. Earl Gillmore, sunbaked, middle-aged and wearing a guitar across his back, had been homeless and unemployed when he set out. "I didn't have the money to do this, but somehow I knew I was supposed to be here. My whole walk has been on faith." Along the way, Gillmore was hired as camp cook and promised a job in Salt Lake City. "I finally know what it means," he said, "to endure to the end." Ted Moore, a Missouri gold miner, gave a more humorous testament of faith. He dug through the pots and pans in his handcart and pulled out a dusty "Pioneer" Barbie doll. "She's going the whole way with me," Moore said. "Every step that I take, Barbie takes."

A few hours before sundown, the wagon train made camp. I had walked only a few miles that day, but I was parched and exhausted. A meal was served. I sat in the dirt and devoured a plate of meat loaf, while around me devout believers watered horses, repaired bent wagon wheels, fed bottles to crying infants. In just a few days, to quote their ancestors, they would cross the mountains and be "safe in Zion." I could not help wishing them well. In their epic trek across Smith's American Eden, they have lost more paradises than they've found.