Smith's marital history had been the subject of frequent historical debate, but until recently Mormon leaders had taken pains to present its founding prophet as happily married to one woman. Now, the church says, "careful estimates put the number between 30 and 40."
The church, officially called the Church of Jesus Christ of Latter-day Saints, disavowed plural marriage in 1890 under pressure from the U.S. government, which had imprisoned polygamists and seized their assets.
It's hard to overestimate Smith's importance to Mormons. He is viewed as a larger-than-life prophet who received special revelations from God. The news that he had taken so many wives, including teens and other men's spouses, rocked some members of the faith, according to Mormon blogger Jana Riess
What's remarkable about the new statement, said Steve Evans, who blogs at By Common Consent, a site that takes an intellectual approach to Mormon history, is that came from the church itself. Twenty years ago, Mormons could be excommunicated for addressing controversial topics like polygamy and the church's former ban on black priests.
But in recent years, with information about Smith's multiple marriages only a Google search away, Mormon church leaders felt pressure to answer questions from the faithful, Evans said. Some Mormons had even left the church after discovering its polygamist past.
"The church is realizing that all of these really controversial topics are being openly discussed on the Internet. So why not put out something that acknowledges the history and tries to get a little bit ahead of it?"
According to the church's essay, Smith had not wanted to take multiple wives, but relented after an angel appeared to him three times between 1834 and 1842. On the angel's last visit, the church said, "the angel came with a drawn sword, threatening Joseph with destruction unless he went forward and obeyed the commandment fully."
As the church's essay notes, Smith also saw his fledgling Mormon movement as a restoration of the "ancient principles" of biblical prophets like Abraham, who practiced plural marriage.
Smith's first wife, however, was not amused. In fact, the church said, "it was an excruciating ordeal for Emma."
Sometime in the 1830s, Smith took his second wife, Fanny Alger, according to the church. They later separated, the church said.
At one point, Emma Smith accepted four of her husbands' plural wives into her household, according to the church. But she likely never knew the full extent of her husband's polygamous unions, LDS officials acknowledge.
Although Smith wed as many as 40 women, he did not necessarily consummate the marriages, the LDS church said. Some might have been "eternity-only sealings," meaning that the relationships were held on reserve for the afterlife.
Most of the women Smith married were between 20 and 40, the church said, but one was as old as 56 and one as young as 14.
"Marriage at such an age, inappropriate by today's standards, was legal in that era, and some women married in their mid-teens," the church said in its online essay.
Helen Mar Kimball, the teen, said her marriage to Smith was "for eternity alone," suggesting the relationship did not involve sexual relations, the church said.
Though controversial, polygamy did have an upside, according to the church: it increased the number of children born in Mormon households.
"A substantial number of today's members descend through faithful Latter-day Saints who practiced plural marriage," the LDS essay said.
The essay is part of a three-part series on the subject, said LDS Church spokesman Eric Hawkins.
A relatively small number of Mormon fundamentalists, who split from the church over polygamy, continue to practice plural marriage, pointing to Smith's original teachings as more authentic than later revisions.
"I kind of look at the gospel as a stream of water, and it's the purest at its source," Anne Wilde of Principle Voices, a Utah-based group that educates the public about polygamy, told CNN four years ago
. "If those are eternal doctrines, then how can man change them?"