Near the edge of Temple Square in Salt Lake City is an unobtrusive statue of a man pulling a wooden handcart, with his family walking beside him. It commemorates a trek more gruelling than the tourists who gawk at it can imagine.
The early Mormons were not popular. They formed an exclusive, polygamous community with a militia and territorial ambitions. The governor of Missouri, Lilburn Boggs, called for them to be "exterminated or driven from the state". Their prophet, Joseph Smith, was shot dead by a lynch mob in 1844. After his murder, his followers embarked on a great exodus.
Some set off in a wagon train and founded a city by the Great Salt Lake in what is now Utah. Others followed. The poorest of them pulled handcarts from Iowa to Salt Lake City-1,300 miles (2,092km) over wilderness and Rocky Mountains. Many died en route. At one point, 1,000 handcarters got stuck in the snow. Brigham Young, the prophet's successor, sent up a mule train from Salt Lake City to rescue them. He saved about 800, but the rest starved or froze to death.
The Church of Jesus Christ of Latter-Day Saints (to use its proper name) is arguably America's most important indigenous religion. It is a universal faith, but also "very American", reckon Richard and Joan Ostling, authors of the excellent "Mormon America: The Power and the Promise". Its history is entangled with America's. Like American settlers, Mormons were pioneers who travelled far for religious freedom. Like America, Mormonism has grown fast. Smith had 26,000 followers when he died. Now he has more than 13m, more than half of them outside America. And within America, by one estimate, Mormonism is the fourth-largest denomination.
As it has grown, it has moved towards the mainstream. Its leaders renounced polygamy in 1890. Its members, following Smith's view that the American constitution was divinely inspired, are patriotic and prone to public service. Mormons are also one of the best-behaved groups in America. Practising ones shun alcohol, cigarettes and even coffee. They work hard, marry, have lots of children and set aside an evening each week for quality time with the family. The 53,000 dark-suited, white-shirted, tie-wearing Mormon missionaries who fish for souls around the world can seem like America personified: earnest, friendly, optimistic, fond of Jesus and eager to tell you about it.
Ruthless campaign strategists now have an incentive to slander Mormonism
Yet many Americans have doubts about Mormonism. Only 53% of non-Mormon Americans think Mormons are Christian, despite the words "Jesus Christ" in the church's name. Many evangelical Protestants think them heretics-the ruder ones regularly heckle Mormon conferences. Some secular Americans voice the opposite complaint: that Mormons are too pious and too likely to knock on your door.
Antipathy towards Mormons is rarer among well-educated Americans (64% of college graduates have a favourable view of them) and among people who actually know a Mormon. But that still leaves a reservoir of suspicion. In a recent Pew poll, 25% of Americans said they would be less likely to vote for a presidential candidate who was a Mormon. Only Muslims and atheists fared worse.
And that could have political consequences, since one of the leading Republican contenders for the presidency in 2008 is a Mormon. Mitt Romney is otherwise a strong candidate. He is tall, handsome, clever and accomplished. His personal life is impeccable: at 60, he is still married to his high-school sweetheart. But he has a big black mark against him: his faith.
He tries to defuse the issue in three ways. First, he quotes John F. Kennedy, who said he was running for president not as a Catholic but as an American. Second, he draws attention to his wholesome private life. And third, he highlights the beliefs Mormons share with other Christians, such as that Jesus Christ is the saviour of mankind. This month he gave a speech on "Faith in America", recalling the time, during the First Continental Congress of 1774, when British troops occupied Boston and someone suggested a prayer.
"There were objections. They were too divided in religious sentiments, what with Episcopalians and Quakers, Anabaptists and Congregationalists, Presbyterians and Catholics. Then Sam Adams [a revolutionary] rose and said he would hear a prayer from anyone of piety and good character, as long as they were a patriot. And so together they prayed, and together they fought, and together, by the grace of God, they founded this great nation." Mr Romney won a standing ovation. But one of his rivals for the Republican nomination refuses to acknowledge that he is a Christian.
For Mormons, the Romney candidacy represents both a challenge and an opportunity, says Michael Otterson, a church spokesman. The surge of media interest gives them a chance to explain their faith to a large audience; but campaign strategists now have an incentive to slander Mormonism. David Magleby, a political scientist at Brigham Young University, suspects that evangelical churches might hold classes on "the cult of Mormonism" just before the South Carolina primary.
So what do Mormons believe? In the Bible, to the extent that it is "translated correctly"; and also in the Book of Mormon, a text that Joseph Smith said he found engraved on thin metal plates after an angel named Moroni showed him where to dig. The book reads like a pastiche of the King James Bible, and contains some startling theology. The story of its origins, however, raises skeptical eyebrows.
It was an ancient text, said Smith, in a language called "Reformed Egyptian". He was able to translate it, he said, using a pair of "seer stones". He worked in a room divided by a curtain, dictating to a scribe who never saw the plates. In all, eight people testified that Smith let them see and touch the plates. He later gave them back to the Angel Moroni, he said.
The Book of Mormon describes how Jesus came to the New World after his resurrection and preached to native Americans. Parts of the text are supposedly a contemporary account of events that took place more than 1,500 years ago. Yet historians note various anachronisms, such as horses, steel and wheat. Neither the archaeological record nor any account besides the Book of Mormon suggests their presence in pre-Colombian America.
Most religions make extraordinary claims. What distinguishes Mormonism from more established faiths is that its founding revelations occurred quite recently. Perhaps because of this, they have been vigorously challenged. For example, in 1835, Smith bought some ancient Egyptian papyruses. One, he said, had been written by Abraham, the Jewish patriarch. He translated it and published it as the Book of Abraham. At the time, no one in America could read hieroglyphics, but when professional Egyptologists first saw facsimiles of Smith's papyrus, they recognised them as fragments from an ancient Egyptian Book of the Dead that bore no relation to his translation.
Critics dismiss Smith as a charming fraud. The Mormon church retorts that an ill-educated farm boy such as he could not simply have made up so sublime a work as the Book of Mormon. Ultimately, the best way to be sure it is true is to pray for guidance, advises the church's website.
Some liberal Mormons, unable to swallow the whole story literally, believe that Smith was divinely inspired but think it unimportant to dwell on the historical details surrounding his revelations. Some sympathetic non-Mormons also admire him. Harold Bloom, a literary critic, describes Smith as "an authentic religious genius, unique in our national history." Mark Twain, less charitably, called the Book of Mormon "chloroform in print".
The church Smith started is strictly hierarchical. At the top is the president, who is considered a prophet. Advising him are two other members of the "First Presidency", beneath which are 12 apostles. Appointments to the top ranks of the church are for life. Since Mormons have few unhealthy vices, their leaders are typically very old: Gordon Hinckley, the current president, is 97.
At lower levels, the church is run by lay volunteers, so it has lower running costs than churches with salaried clergy. Since good Mormons tithe-that is, they give a tenth of their income to the church-the church is colossally wealthy, though its finances are secret. A decade ago, the Ostlings estimated its assets at $25-30 billion, but who knows? What is certain is that it owns several companies (in publishing, food-processing and other wholesome areas), spends a fortune helping the victims of floods and famine, and builds new temples at an impressive clip.
The church believes in "continuous revelation", so its doctrines can evolve. Take polygamy. Smith had at least 28 wives. He said polygamy was God's will. The rest of America was horrified. In 1887 Congress passed a law to dissolve the Mormon church. In 1890 the Supreme Court upheld it. Shortly afterwards, the church's fourth president banned polygamy. Within six years, Utah had won statehood.
A more recent revelation concerned race. The very early Mormons were quite liberal for their time: their neighbours in Missouri complained that they did not own slaves. But Mormon scriptures say some harsh things about dark-skinned people and until 1978 blacks were barred from the priesthood, which, in Mormon parlance, includes more or less any devout male over the age of 12. This rule made it tough to win converts in, say, Brazil, let alone Africa. But in 1978 a new revelation revoked the colour bar.
Asked why the bar ever existed, Russell Ballard, an apostle, says simply: "We don't know." Elder Ballard is pleased that the church is now more open: he gushes about its growth in Ghana and Nigeria. And though Smith said God told him that other churches were "all wrong", Elder Ballard is more tactful. Christians from other churches can keep everything they have, he says, but if they become Mormons they will get something extra. He stresses the good relations Mormons enjoy with other churches, and the values they share. An amiable father of seven and grandfather of 43, he is keen to talk about the need to preserve the traditional family as American morals crumble.
A Mormon marriage, if performed in a temple, is eternal. Husband and wife are reunited in heaven, along with their extended family. This view of kinship helps explain why Mormons are so interested in genealogy. They like to find out who their ancestors were so they can perform a baptism for them, and give them the option of becoming Mormons posthumously.
The church's Family History Library in Salt Lake City has the largest collection of genealogical data in the world. Mormon researchers have amassed 2.4m rolls of microfilm of births, deaths and marriages. They collect Chinese clan records and transcribe African oral genealogies. (They used to do baptisms for Jewish Holocaust victims, but stopped when living Jews complained.) Visitors to the centre can research their own ancestry, or simply admire the industry that went into discovering that Brigham Young is George Bush's fifth cousin, five times removed.
Wedded as they are to traditional mores, Mormons tend to vote Republican. Not always: the leading Democrat in the Senate, Harry Reid, is a Mormon. And the church is careful to remain politically neutral, except on what it calls moral issues. (It opposes gay marriage, for example.) But still, the typical Mormon congressman is Chris Cannon, a Utah Republican whose district has the highest number of children of any in the country. The American Conservative Union gives him a 100% rating. His views on the family are pretty much the opposite of those of Nancy Pelosi, the top Democrat in the House of Representatives, whose San Francisco district has the lowest number of children. But Mr Cannon's conservatism is nuanced: he supports more welcoming immigration laws even if it hurts him politically.
Many Mormons like the idea that one of their own might become president. But some have mixed feelings. Ryan Decker, an economics student at Brigham Young, frets that Mormon missionaries abroad are already often seen as somehow representative of American foreign policy. With a Mormon in the White House, that confusion would be harder to dispel.
That would matter, because so many Mormons go on missions for a couple of years. Among the devout, especially men, it is expected. They work in pairs, partly for safety, partly to keep each other in line. Missionaries must live simply, rise early and follow an arduous regimen of prayer, study and accosting strangers. Some find it tough; others, formative.
Stephen Covey, a self-help guru whose book "The Seven Habits of Highly Effective People" has sold 15m copies, went to Britain as a missionary when he was 20. "It helped me learn how to speak in public and interact with an audience," he says. He held meetings that sometimes drew hundreds, he recalls. Mitt Romney was less successful. As a missionary in France, he won "no more than a handful" of converts, he told a biographer, Hugh Hewitt.
A century and a half ago, relations between Mormons and their neighbours were often bloody. Now, they are pretty good. Sober, diligent, nice people are hard to hate. To find tensions between Mormons and non-Mormons, you have to go where the two groups compete for power.
Ironically, Mormonism's Mecca is such a place. Mormons are no longer a majority in Salt Lake City: with large families, they tend to live in the suburbs. So the city now has a non-Mormon mayor, Rocky Anderson. He says that relations between the two groups are "quite strained". Thanks to a Mormon-dominated city council, drinking laws are finicky. If you want to booze without eating, you can either buy extra-watery beer or join a private club.
The mayor cites a long-running dispute with the church over public access to a block in the centre of town that it bought from the city a few years ago. Tempers have erupted over this, but not fist-fights. Mr Anderson also complains that the church opposes gay rights. That is a big problem for gay Mormons, but less so for gay gentiles with Mormon neighbours. Salt Lake City has been rated one of the 51 "fabulous" places to be gay in America.
Tensions exist within the church, too. Some Mormons find the rules hard to live by. Others find the hierarchy stultifying. Paul Toscano, a lawyer who was excommunicated for criticising church leaders, says that 19th-century Mormonism was to religion what Bach is to music: complex and rich. Now, he says, the church is run by corporate types, not theologians, and its teachings have become simple and bland, "like people dancing the polka".
Some Mormons just focus on what one might call "cultural Mormonism"-clean living and family values-while glossing over what the scripture actually says. Mr Toscano recalls that, when he was a young man about to go on his mission, he mentioned to his bishop (roughly the equivalent of a parish priest) that Joseph Smith was a polygamist. The man's face froze in genuine surprise. He said he could not let Mr Toscano go on a mission spreading false doctrine. "He was an idiot," says Mr Toscano of his former bishop.
The biggest threat to the church's image comes from the hundreds of sects that have splintered from it. The most notorious is led by Warren Jeffs, who ruled a remote town on the Utah-Arizona border like a priest-king until he was arrested last year for abetting the rape of an under-age girl, whom he had ordered to marry her cousin.
Mr Jeffs told his followers that men could go to heaven only if they had multiple wives. So there were never enough women to go around, and Mr Jeffs started expelling adolescent boys for minor offences. Hundreds of these "Lost Boys" now live in the nearest towns. They can usually earn a living, having typically worked on building sites since they were ten.
Kevin (he won't give his surname) says he was thrown out of the sect two years ago, when he was 17, for "playing video games, stuff like that". He now realises that Mr Jeffs's teachings were "crap". He split families. One day he might judge a man unworthy of his wives and children and give them all to another man. He banned television, but Kevin's dad hid theirs in the closet. Kevin did not watch Mr Jeffs's trial, but says: "I hope they convict him of something." They did: he got ten years to life.
Mainstream Mormons are sometimes confused with such groups. But the better they are known, the less often it happens. Mr Romney might help scotch the association with polygamy: unlike nearly all the other serious Republican presidential candidates, he has had only one wife.