Turning to the family Bible, Smith came to a verse in James that struck him powerfully: "If any of you lack wisdom, let him ask of God ... and it shall be given him." Inspired, Smith went into a grove of trees to pray. As he began, a dark force seized him—until, Smith said, God himself intervened. "At this moment of great alarm," Smith recalled, "I saw a pillar of light exactly over my head, above the brightness of the sun, which descended gradually until it fell upon me." God and Jesus appeared and delivered a startling message: he shouldn't join any of the churches of the world, for they had long ago fallen away from Christ's true Gospel.

This experience, known as the First Vision by Smith's followers, ultimately gave the world a new faith: Mormonism, or the Church of Jesus Christ of Latter-day Saints, which now has more than 12 million members and, thanks to the vigorous missionary tradition started by Smith himself, is one of the fastest-growing Christian denominations in the United States.

Prophet and polygamist, mesmerizer and rabble-rouser, saint and sinner: Smith is arguably the most influential native-born figure in American religious history, and is almost certainly the most fascinating. This year marks the 200th anniversary of his birth, and the bicentennial is prompting fresh and searching looks at Smith, the faith he built and the legacy he left behind. The church is opening Smith's life and contributions to research—a new stance for an institution whose early experience with persecution has often made it defensive and secretive. This summer, Brigham Young University hosted a six-week multifaith seminar, funded by the National Endowment for the Humanities, and Smith's papers are now being consolidated and published.

Smith's times are much like our own, and his story has a particular resonance in the first years of the 21st century. Like us, he lived in an era of evangelical energy, deep patriotism, economic transformation, sharp political divisions and anxiety about foreign forces' inflicting harm on the homeland. Smith's teachings placed America at the center of existence at just the moment in our history—in the wake of the successful War of 1812—when nationalism was on the rise.

From Mitt Romney, the Republican governor of Massachusetts and a 2008 presidential prospect, to Harry Reid, the Democratic leader in the Senate, Mormons are increasingly visible in different spheres of American society, particularly in politics and the Fortune 500. Traditionally conservative but not really part of the religious right, the church opposes gay marriage and abortion (unless the mother's life is in danger or in cases of rape or incest). In the emotional case of Terri Schiavo earlier this year, however, the church diverged from many conservative Christians when it responded to news media by saying, "Members should not feel obligated to extend mortal life by means that are unreasonable." There is also room for policy differences among public figures who happen to be Mormon: Romney opposes fetal-stem-cell research, while Sen. Orrin Hatch of Utah supports it. Meanwhile, the faith's traditional views on morality and the family are fueling its rapid growth in the developing world, where, despite a broad feeling of global anti-Americanism, the church is expanding even more rapidly than it is within the United States.