Mormon leaders have finally admitted that the church's founder and prophet, Joseph Smith, took as many as 40 wives, some already married and one only 14 years old.

Smith, who wrote the Book of Mormon and established the Church of Jesus Christ of Latter-day Saints, had been portrayed in church materials as a loyal partner to his loving spouse Emma.

The church's acknowledgement is part of an effort to be more open about its history as members increasingly encounter claims about the faith on the internet.

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Polygamous: The Mormon church has admitted that its founder Joseph Smith (right) had 40 wives - including 14-year-old Helen Kimball (pictured left much later in life)

'Difficult': An essay published by the church describes Smith's reluctance to engage in plural marriage - and says the process was 'excruciating' for his first wife, Emma, depicted above

Many Mormons, especially those with polygamous ancestors, say they were well aware that Smith's successor, Brigham Young, practiced polygamy when he led the flock in Salt Lake City, The New York Times reports.

However, they did not know the full truth about Smith.

'Joseph Smith was presented to me as a practically perfect prophet, and this is true for a lot of people,' said Emily Jensen, a blogger and editor in Farmington, Utah, who often writes about Mormon issues.

She said the reaction of some Mormons to the news was similar to the five stages of grief, 'this is not the Joseph Smith I love'.

According to the church, Smith was unlikely to have had sexual relations with all of his wives, as some were 'sealed' to him for the next life. But the multi-marriages were said to be 'an excruciating ordeal', for his wife.

Most of Smith's wives were between the ages of 20 and 40, but he married Helen Mar Kimball, a daughter of two close friends, 'several months before her 15th birthday.' According to 'careful estimates', the church said Smith had 30 to 40 wives.

Smith also wed women who were already married, some to men who were his friends and followers.

The Church of Jesus Christ of Latter-day Saints, as the Mormon Church is formally known, has posted 12 essays on its website over the last year on contentious topics.

Public admission: The Church of Jesus Christ of the Latter-day Saints had stayed silent on the issue of Joseph Smith's polygamy for years. Pictured is a statue of Smith and his first wife, Emma, in front of the church's Salt Lake City headquarters

Elder Steven E. Snow, the church historian and a member of its senior leadership, has reportedly said, 'There is so much out there on the Internet that we felt we owed our members a safe place where they could go to get reliable, faith-promoting information that was true about some of these more difficult aspects of our history.

'We need to be truthful, and we need to understand our history,' Elder Snow said. 'I believe our history is full of stories of faith and devotion and sacrifice, but these people weren't perfect.'

The essay on 'plural marriage' in the early days of the Mormon movement in Ohio and Illinois says polygamy was commanded by God. It goes on to say it was then revealed to Smith and was reluctantly accepted.

Abraham and other Old Testament patriarchs had multiple wives, and Smith preached that his church was the 'restoration' of the early, true Christian church.

An essay published by the church describes how Smith said he was visited three times by angels between 1834 and 1842 who commanded him to marry more women, despite him already having a wife, Emma.

The third time, the essay says: 'The angel came with a drawn sword, threatening Joseph with destruction unless he went forward and obeyed the commandment fully.'

Ban: Polygamy was outlawed by the Mormon church in 1890. Pictured are church leaders around that time, including Wilford Woodruff, the leader who ended the practice

Other writings posted by the church in the past couple of years have addressed sacred undergarments worn by devout members; a past ban on black men in the lay clergy; and the misconception that Mormons are taught they'll get their own planet in the afterlife.

The articles about Smith's wives during the 1830s and 1840s in Kirtland, Ohio, and Nauvoo, Illinois, comes about 10 months after the church acknowledged polygamy was widely practiced among its members in the late 19th century.

'As a collection, these are remarkably revealing articles, continuing the new open and transparent philosophy of historical writing,' said Armand Mauss, a retired professor of sociology and religious studies at Washington State University.

The information will be surprising to many Latter-day Saints who either didn't know or were encouraged to dismiss speculation as anti-Mormon propaganda, Mauss said.

Splinter groups who call themselves fundamentalist Mormons still practice plural marriage, including Warren Jeffs' sect on the Utah-Arizona border.

Latter-day Saints began practicing polygamy after Smith received a revelation from God. He took his first plural wife in 1830 in Ohio, three years after he married his first wife, Emma, an earlier article revealed.

He and his first plural wife separated, but he renewed the practice a decade later in Illinois, which is where he married the teenager.

The essay noted that while inappropriate by today's standards, marriage among teen girls was legal at the time.

The article acknowledges that many details about polygamy in early Mormonism are hazy because members were taught to keep their actions confidential. But research has indicated that Smith's marriage to the young girl might not have involved sex.

'Remarkable, revealing': Experts have commented that the decision to address such issues is an unusually transparent move by the church's leaders. Pictured is Salt Lake Temple, the Mormon faith's most important church

Some plural marriages were designed to seal the man to the woman for eternity only, and not life and eternity as Mormons believe, the article says. Those types of marriages didn't seem to involve sex.

Little is known about Smith's marriages to the already-married women, the article says. They also might have been the type of unions that didn't involve sex.

Plural marriage was an 'excruciating ordeal' for Emma Smith and confounding for some men, too, the article says. Some people left the faith, and others refused to take multiple wives while remaining Latter-day Saints.

When Latter-day Saints trekked cross-country to Utah in 1847, nearly 200 men and more than 500 women were in plural marriage, it says.