Read today that Willard *Mitt* Romney's ancestor was Parley P Pratt (Jared Pratt b 1769 >Parley Parker Pratt b 1807 Otsego NY (brother was Orson Pratt) >  Helaman Pratt b 1846 > Anna Amelia Pratt m Gaskel Romney. He wrote about him in his book "Turnaround" - From Salon.

The precipitous mountain pass that led the [Mormon] pioneers down into the Salt Lake Valley and still is the route of access from the east on Interstate 80, was first explored by my great-grandfather, Parley P. Pratt,” Mitt Romney cheerfully writes in “Turnaround,” the airport bookstore leadership manual he wrote in 2004 while governor of Massachusetts.

“He had worked a road up along ‘Big Canyon Creek’ as an act of speculation when his crop failed in the summer of 1849. He charged tolls to prospectors making their way to California at the height of the Gold Rush and even had a Pony Express station commissioned along his pass.”

Sounds pretty cheerful, doesn't it? But what's missing is Parley Pratt, polygamist, who was accused of marrying an already married and not divorced woman, who was shot dead in Arkansas, and whose death probably had a strong hand in the lurid story of the Mormon's massacre of the Fancher party from Arkansas.

Romney doesn’t add — and why should he? — that Pratt was murdered in 1857, by the husband of a woman he took as one of his “plural wives.” (His ninth.) Pratt was in San Francisco proselytizing and promoting polygamy. The woman converted and eloped with Pratt, then pretended to renounce Mormonism in order to get her children from her parents, where her estranged husband had sent them. The husband tracked Pratt from California to Arkansas, and shot him dead when it became clear that he could not have Pratt jailed. This incident contributed to the general sense of apocalyptic paranoia among the Mormon community that led to the Mountain Meadows Massacre, in which Mormon settlers — acting, according to some, on orders from Brigham Young — killed an entire wagon train of families on their way to California. There were rumors, before the Mormon militia attacked the wagon train, that Pratt’s killer was among the mostly wealthy Arkansans in the train. The Mormons attempted to blame the murder of children and women on Indians, though Mark Twain and others believed that the “Indians” were likely Mormons in war paint. (Archaeological evidence — dug up, embarrassingly, during preparations for the Salt Lake City Winter Olympics — supports that theory.)

The massacre is the bloodiest and most disturbing moment in Mormon Church history, and also one of the rare moments in the 19th century when the Mormons were the perpetrators and not the victims of violence.

Here's what wikipedia says about it.

While returning from a horseback missionary trip to the southern United States in 1857, Pratt was being tracked by Hector McLean. McLean was the legal husband of one of Pratt's plural wives, Eleanor McLean. Pratt had met Eleanor McLean in San Francisco, California, where Pratt was presiding over a church mission. In San Francisco, Eleanor had joined the LDS Church and had also had her oldest sons baptized. Hector rejected Mormonism and opposed his wife's membership in the church. The dispute over the church led to the collapse of the marriage.[3] Fearing that Eleanor would abscond to Utah Territory with their children, Hector sent his sons and his daughter to New Orleans to live with their grandparents.[4] Eleanor followed the children to New Orleans, where she lived with them for three months at her parents' house. Eventually, she and the children left for Utah Territory; she arrived in Salt Lake City on September 11, 1855.[4] Eleanor McLean was employed in Pratt's home as a schoolteacher, and on November 14, 1855, she and Pratt underwent a "celestial marriage" sealing ceremony in the Endowment House.[4] She was the twelfth woman to be sealed to Pratt. Though for religious reasons Eleanor considered herself "unmarried", she was not legally divorced from Hector at the time of her "celestial marriage" to Pratt.[5][6][7]

Upon learning of his wife's actions, Hector McLean pressed criminal charges, accusing Pratt of assisting in the kidnapping of his children.[8] Pratt managed to evade him and the legal charges, but was finally arrested in Indian Territory (now Oklahoma) in May 1857.[9] Pratt and Eleanor were charged with theft of the clothing of McLean's children.[10] (The laws of that time did not recognize the kidnapping of children by a parent as a crime.) Tried before Judge John B. Ogden, Pratt was acquitted of the charges because of a lack of evidence.[10] However, shortly after being secretly released, on May 13, 1857, Pratt was shot and stabbed by Hector McLean on a farm northeast of Van Buren, Arkansas.[10] As a result of the attack, Pratt died two and a half hours later from loss of blood.[10] As he was bleeding to death, a farmer asked what he had done to provoke the attack. Pratt responded, "He accused me of taking his wife and children. I did not do it. They were oppressed, and I did for them what I would do for the oppressed any where."[10] Pratt was buried near Alma, Arkansas, despite his personal desire to be buried in Utah.

Some historians view Pratt's death as simply the act of a jealous husband who was deeply angered by a man that had "run off" with his wife.[11] A 2008 Provo Daily Herald newspaper article characterized McLean as a man that had "hunted down" Pratt in retribution for "ruining his marriage".[12] A 2008 Deseret News article described McLean as a man that had "pursued Pratt across Missouri, Oklahoma and Arkansas, angry that his estranged wife, Eleanor, had become Pratt's 12th wife."[13] But many Mormons viewed Pratt's death as a martyrdom, a view first expressed in Pratt's dying words.[14] (But according to LDS church records, his dying words were not recorded until 38 years after his death.)[15] In the present day, Pratt's defenders still characterize the circumstances of Pratt's death as religious martyrdom. For example, a 2007 article in the Deseret Morning News stated that "Pratt was killed near Van Buren, Ark., in May 1857, by a small Arkansas band antagonistic toward his teachings".[16] Historian Will Bagley reports that McLean and two friends tracked Pratt after he was secretly released by Van Buren's magistrate.[17] Brigham Young compared Pratt's death with those of Joseph and Hyrum Smith,[18] and many Mormons blamed the death on the state of Arkansas, or its people.[19]

Due to his personal popularity and his position in the Council of the Twelve, Pratt's murder in Arkansas was a significant blow to the Latter-day Saint community in the Rocky Mountains, when they began hearing about it in June 1857.[20] The violent death of Pratt may also have played a part in events leading up to the Mountain Meadows massacre a few months later.[21] This massacre resulted in the deaths of 120 people from the Baker–Fancher party travelling to Southern California along the Mormon Road (a portion of the Old Spanish Trail). After the massacre, some Mormons circulated rumors throughout the southern Utah Territory that one or more members of the party had murdered Pratt,[22] poisoned creek water which subsequently sickened Paiute children,[23] and allowed their cattle to graze on private property.[24]

You can read about the Mountain Meadows Massacre and Parley Pratt in this book written by one of Mitt Romney's 19 wives, who felt that polygamy did not support the sanctity of marriage. Start reading on page 237.  From p 243

The Arkansas members of the train, also, were objects of Mormon vengeance. Parley P Pratt, one of the twelve apostles, and also one of the brightest intellectual lights of the Church of the Latter-Day Saints, was sent on a mission to California, where he proselyted with such vigor that many converts were made;  among them a Mrs Eleanor McLean, wife of one Hector McLean, and the mother of three children, who was induced to embrace Mormonism and polygamy as embodied in the person of the seductive apostle. The command to "leave all and follow me" was readily obeyed, especially as she was personally to add to the minister's present pleasure and future glory, by becoming one of his numerous plural wives.

As there was no authority to marry them in a "legal" manner in this Gentile state, they were obliged to defer that ceremony until their arrival in *Zion*. But in cases like this, which were often occurring to the missionary saints, it was considered quite proper for the pair, who were in haste to wed, to "covenant together" and thereafter to be regarded as man and wife, without ministerial or judicial aid, until such time as they could celebrate their nuptials in the presence of saintly witnesses and after the 1 saintly fashion. This covenant the Apostle Pratt and Mrs McLean were not slow to make .

The news soon reached the husband that his wife was going to Utah with the Mormon Elder, and intended taking teh children with her. This last design McLean frustrated by sending them to some relatives in one of the Southern States. He then informed his wife that she was at liberty to go where she chose, but that she must go alone, as he had placed the children beyond her reach.

She came to Utah and immediately on her arrival was sealed to Parley, after having lived under a covenant with him for months. The mother-heart, however, yearned for her children; neither her new religion nor the fractional part of an apostle could fil the voide left by the separation from them and she determined to gain possession of them and bring them also to Utah. After much entreating, she succeeded in inducing her new husband to go to the States with ehr for the purpose of finding them. She went alone to the place where her children were at school, leaving Pratt in Arkansas-which by the way, was her husband's home. On reaching the town where her children were, she was obliged to assume a disguise, as McLean was there, having followed his children from California. She used very stratagem to obtain them, but only succeeded in carrying away one. She quicky made her way with him to Arkansas and joined Parley, who was awaiting her there. Together they started to return to Utah, but were overtaken by McLean, who, maddened by the breaking up of his home, the seduction of his wife, and the abduction of his child, determined to wreak summary vengeance on the man who, under the guise of religion, and in the name of the Lord, whom he constantly blasphemed by taking his Holy name upon his polluted lips, had wrecked his whole life's happiness.

Being examined before a magistrate, Mrs McLean Pratt assumed all the responsibility of the children, and the Apostle was honorably discharged. His friends, however, apprehended danger, and advised him to escape, if he could, for McLean was a violent man. They also offered him a couple of revolvers for his defence.

The Apostle fled, but McLean was on his trail. At length the wronged husband came within sight of his enemy and pursued him like the avenger of blood. Pratt left the public road, endeavoring to reach a house not far distant, but McLean was too swift for him. Following him closely with revolver drawn, he fired at the saintly seducer, but failed to touch him. Furious at Pratt's escape, McLeans urged forward his horse, and as he passed the enemy, made a lunge with his bowie-knife, and gvae him a fatal thrust in his side. The wounded man fell from his horse, instanttly and McLean fired again at the guilty wretch as he lay bleeding on the ground and the ball penetrated his breast. ... the people of Arkansas upheld McLean and it was considered that he had only done his duty of ridding the world of such a wolf in sheep's clothing.

But the Mormons were deeply infuriated; they held every Arkansas man personally responsible for the murder of their third apostle.... the fact that Pratt had brought his death upon himself was not taken into consideration.

Now go read the rest about the Fancher party from Arkansas and how they were slaughtered at Mountain Meadows in Utah.  There is also an excellent book on the subject called "Massacre at Mountain Meadows"

Mark Twain wrote about the Mountain Meadow Massacre in "Roughing it"

A 'revelation' from Brigham Young, as Great Grand Archee or God, was dispatched to President J. C. Haight, Bishop Higbee and J. D. Lee (adopted son of Brigham), commanding them to raise all the forces they could muster and trust, follow those cursed Gentiles (so read the revelation), attack them disguised as Indians, and with the arrows of the Almighty make a clean sweep of them, and leave none to tell the tale; and if they needed any assistance they were commanded to hire the Indians as their allies, promising them a share of the booty. They were to be neither slothful nor negligent in their duty, and to be punctual in sending the teams back to him before winter set in, for this was the mandate of Almighty God."

The command of the "revelation" was faithfully obeyed. A large party of Mormons, painted and tricked out as Indians, overtook the train of emigrant wagons some three hundred miles south of Salt Lake City, and made an attack. But the emigrants threw up earthworks, made fortresses of their wagons and defended themselves gallantly and successfully for five days! Your Missouri or Arkansas gentleman is not much afraid of the sort of scurvy apologies for "Indians" which the southern part of Utah affords. He would stand up and fight five hundred of them.

At the end of the five days the Mormons tried military strategy. They retired to the upper end of the "Meadows," resumed civilized apparel, washed off their paint, and then, heavily armed, drove down in wagons to the beleaguered emigrants, bearing a flag of truce! When the emigrants saw white men coming they threw down their guns and welcomed them with cheer after cheer! And, all unconscious of the poetry of it, no doubt, they lifted a little child aloft, dressed in white, in answer to the flag of truce!

The leaders of the timely white "deliverers" were President Haight and Bishop John D. Lee, of the Mormon Church. Mr. Cradlebaugh, who served a term as a Federal Judge in Utah and afterward was sent to Congress from Nevada, tells in a speech delivered in Congress how these leaders next proceeded:

"They professed to be on good terms with the Indians, and represented them as being very mad. They also proposed to intercede and settle the matter with the Indians. After several hours parley they, having (apparently) visited the Indians, gave the ultimatum of the savages; which was, that the emigrants should march out of their camp, leaving everything behind them, even their guns. It was promised by the Mormon bishops that they would bring a force and guard the emigrants back to the settlements. The terms were agreed to, the emigrants being desirous of saving the lives of their families. The Mormons retired, and subsequently appeared with thirty or forty armed men. The emigrants were marched out, the women and children in front and the men behind, the Mormon guard being in the rear. When they had marched in this way about a mile, at a given signal the slaughter commenced. The men were almost all shot down at the first fire from the guard. Two only escaped, who fled to the desert, and were followed one hundred and fifty miles before they were overtaken and slaughtered. The women and children ran on, two or three hundred yards further, when they were overtaken and with the aid of the Indians they were slaughtered. Seventeen individuals only, of all the emigrant party, were spared, and they were little children, the eldest of them being only seven years old. Thus, on the 10th day of September, 1857, was consummated one of the most cruel, cowardly and bloody murders known in our history."

The number of persons butchered by the Mormons on this occasion was one hundred and twenty.

Back to the Salon article, which notes that

There were rumors, before the Mormon militia attacked the wagon train, that Pratt’s killer was among the mostly wealthy Arkansans in the train. The Mormons attempted to blame the murder of children and women on Indians, though Mark Twain and others believed that the “Indians” were likely Mormons in war paint. (Archaeological evidence — dug up, embarrassingly, during preparations for the Salt Lake City Winter Olympics — supports that theory.)

So why did Romneys' family go to Mexico.? Because the town where they were was not favorable to polygamy (not to mention that practicing polygamy was a federal crime)

Polygamy is the reason George Romney was born in Mexico. The Romneys had been Mormons since way back. Carpenter Miles Archibald Romney, along with his family, converted in 1837, after hearing the story of Joseph Smith finding those golden plates in upstate New York. The Romneys moved to Smith’s Mormon community in Nauvoo, Ill., in 1841, and had Miles Park Romney in 1843. Miles Park became a builder, moved to Utah, married one woman, did mission work in England, returned to Utah and married another woman on orders from Brigham Young himself. He became quite prominent in the Mormon community, building Brigham Young’s gigantic home and helping to defeat a congressional anti-polygamy law. Romney and his three wives and various children were then sent to settle St. Johns, Ariz., as part of the church leadership’s plan to settle across the entire American West. St. Johns was not particularly welcoming to the Mormon newcomers, and after various threats to hang the lot of them, the Romney clan was told — ordered, actually — to try Mexico instead.

So they created a new Mormon colony, Colonia Juarez, and after some hardship, did reasonably well for themselves. Miles even took another wife seven years after the church officially “banned” the practice of plural marriage. Gaskell Romney, Miles Romney’s son with his first wife, Hannah Hood Hill, became a builder as well, and married one woman: Anna Amelia Pratt, granddaughter of Parley. They gave birth to George a few years before the Mexican Revolution forced the whole colony back to the United States.

Here's some more background on that. Bear in mind that at the time polygamy was made a federal crime and those who practiced it were ineligible for public office.

In 1884 a federal grand jury in the territorial capital of Prescott indicted five prominent St. Johns Mormons for polygamy: Ammon Tenney, William Flake, Peter Christofferson, Christopher Kempe and James Skousen.

Their trial was the first of its kind in Arizona, noted JoAnn Bair and Richard Jensen in their article "Prosecution of the Mormons in Arizona Territory in the 1880s," published in the University of Arizona's historical periodical "Arizona and the West" in 1977.

Flake and Skousen pleaded guilty and received six-month sentences in the Yuma territorial prison.

But Tenney, Kempe and Christofferson, who refused to plead guilty, were convicted in December 1884 and sentenced to 3.5 years in the new House of Corrections in Detroit.

Within two months of the sentencings, Mormon Church President John Taylor was publicly encouraging Arizona followers to organize settlements in Mexico.

Bishop Udall was the only man who escaped prosecution because authorities couldn't find his second wife.

Emboldened by the convictions, federal authorities revived the perjury charges against Romney, Crosby and Udall in 1885.

Deciding he couldn't get a fair trial, Romney skipped bail and fled to Mexico with his then four wives and their children. William Flake, the co-founder of Snowflake, had to find a way to cover Romney's $2,000 bond.

Incidentally, how did Miles Romney's wife, Hannah Hood Hill Romney take to being one of multiple wives? Gee, she didn't like it.

Miles returned to Utah in October 1865, meeting his 2-year-old daughter for the first time. The family was poor, possessing a small cook stove, a bed, three chairs and a small table. Miles, a carpenter, bought land and built a two-room wooden house. Hannah became pregnant again, and a second daughter was born.
      "We were happy," Hannah recalled, in an autobiography written for her family when she was 80 years old. "We had two sweet little girls to bless our home and make it more happy and they bound us together in love and union."

      Addition to marriage
      It was then, in 1867, that Miles P. Romney had a fateful meeting with Young.
      "Brother Miles P., I want you to take another wife," Young requested, according to Hannah's autobiography.
      Miles faced the choice of obeying U.S. law, under which polygamy was illegal, or the head of The Church of Jesus Christ of Latter-day Saints. He chose the church.
      Hannah was distraught.
      "I felt that was more than I could endure, to have him divide his time and affections," Hannah wrote later. "I," she wrote, "used to walk the floor and shed tears of sorrow. If anything will make a woman's heart ache, it is for her husband to take another wife, but I put my trust in my Heavenly Father and prayed and pleaded with him to give me strength to bear this great trial."
      Then Hannah performed her duty: She prepared a room for her husband's new wife, Caroline Lambourne. Hannah wrote, "I was able to live in the principle of polygamy and give my husband many wives." But her despair deepened when her younger daughter died at 10 months.
      Soon, Young gave Miles and his two wives a new mission: Sell your home, and move to the southern Utah town of St. George. The new settlement about 300 miles south of Salt Lake was in a vast desert, surrounded by red-toned ridges in a region where summer temperatures often topped 100 degrees.
      Young prophesied that, "There will yet be built between these volcanic ridges, a city, with spires and towers and steeples, with homes containing many inhabitants." The Romneys sold their Salt Lake City home and moved to St. George, where they lived "in a little shanty, a small board room and a wagon box," Hannah wrote.
      From the shanty, the Romneys wrote themselves into church history as builders. Miles played a major role in the construction of the St. George Temple. Then, Brigham Young hired Miles to build a two-story addition to his winter home in St. George. Miles took on the task with zeal, constructing one of the most lavish residences in Utah, a sandstone brick dwelling with an elaborate porch painted red and green. The restored home is visited today by Mormons from around the world, who are told of Miles's role in building the house. Pictures of Young and Romney hang in an adjoining building.
      But while Miles was prospering as a builder, he had increasing trouble handling two wives. Hannah wrote that Caroline "was very jealous of me.... She wanted all my husband's attention. When she couldn't get it there was always a fuss in the house. (Miles), being a just man, didn't give way to her tantrums."
      Miles and Caroline had two children, William George Romney and Martha Diana Romney, whom Hannah helped to care for. But Caroline was not satisfied. She asked Young for permission to return to her parents in Salt Lake City. The separation was "the severest trial ever experienced" by Miles, according to "Life Story of Miles Park Romney," written by his son, Thomas. Miles and Hannah "made a special trip of three hundred miles by wagon to try to induce Carrie to return to her home in Saint George. But all their pleadings were in vain," and a divorce was granted, according to the biography.
      Miles, meanwhile, was climbing in prominence in the church. He was given a new responsibility: defeat a congressional effort to enforce antipolygamy prohibitions.
      Miles and four other Mormon leaders signed a letter stating that "the Anti-polygamy bill ... is unconstitutional and is an act of special legislation and ostracism, never before heard of in a republican government and its parallel hardly to be found in the most absolute despotisms, disfranchising and discriminating, as it does, 200,000 free and loyal citizens, because of a particular tenet in their religious faith."
      Miles and the others said the legislation violated the Declaration of Independence's guarantee that all men had the rights of "life, liberty and the pursuit of happiness" and the Constitution's guarantee of freedom of religion.
      The lobbying paid off and the bill died in the Senate, but other anti-polygamy laws remained on the books.
      For a brief time, with Caroline having left, Miles and Hannah were once again in a single-wife marriage. It was then, in 1871, that Hannah gave birth to Gaskell Romney, the grandfather of Mitt Romney.
      Two years after Gaskell's birth, however, Miles met the fair-skinned Catharine Cottam, who had flowing hair, a serene smile, and was described by her brother as the "prettiest girl in St. George." Miles married Catharine in Salt Lake City on Sept. 15, 1873.
      Hannah, seven months pregnant, did not attend the wedding. Instead, she prepared a room for Catharine, whom she called "a girl of good principles and a good Latter-day Saint."
      "I cannot explain how I suffered in my feelings while I was doing all this hard work, but I felt that I would do my duty if my heart did ache," Hannah wrote.
      Two months after Miles and Catharine were married, the child of Miles and Hannah died during delivery. Hannah blamed herself.
      "I felt I had caused it by doing so much hard work," Hannah wrote.
      Nearly four years later, Miles married again, taking as his wife Annie M. Woodbury, a schoolteacher.
      Miles's life in St. George with Hannah, Catharine and Annie briefly settled into a comfortable, devout routine. But church leaders in Salt Lake City intervened, devising a plan to plant Mormon communities in an arc throughout the West. Miles was told by church leaders to uproot his family and help settle the town of St. Johns, Ariz.
      The journey of almost 500 miles was harrowing, requiring the wagon trains to skirt the northern rim of the Grand Canyon.
      "Here you can see the river hundreds of feet below you winding its way between perpendicular banks of solid rock without a tree to be seen and devoid of vegetation," Catharine wrote her parents, as quoted in a volume compiled by her great-granddaughter Jennifer Moulton Hansen, titled, "Letters of Catharine Cottam Romney, Plural Wife."
      Finally, the Romneys arrived in St. Johns. It was a sparsely settled town, a Wild West amalgamation of gun-toting farmers and laborers, including American Indians and Mexicans, who were especially resentful of new settlers such as the Mormons. The local newspaper, the Apache Chief, urged on May 30, 1884, that "the shotgun and rope" be used to get rid of Mormon settlers.
      "Hang a few of their polygamist leaders such as ... Romney ... and a stop will be put to it," the newspaper said.
      Catharine began to fear her surroundings, writing, "I believe there are some as wicked people here as can be found anywhere on the footstool of God."
      The tensions accelerated as local authorities sought to try Romney on charges of polygamy. To avoid prosecution, Miles sent Catharine and Annie into hiding.
      But authorities brought new charges, alleging that Miles lied about having title to his land. One night, a marshal arrived at the Romney home after midnight, demanding that Miles surrender.
      "The marshal had a gun in one hand and handcuffs in the other," Hannah wrote.

      A colony in Mexico
      Miles fled to Utah, where he was told by church leaders "to go to Old Mexico and build a city of refuge for the people that would have to go there on account of persecutions of polygamy," Hannah wrote. Miles agreed and decided it was safest to go with only one of his wives, Annie. He left behind Hannah and Catharine and their children, hoping they would reunite in the coming months.

P.S. Did you know that it was Parley Pratt who said that blacks are cursed by God and couldn't be part of the mormon priesthood?(See book "Black and Mormon"  It wasn't until 1978  that the Mormon church reversed that after the guy in charge had a revelation from God (that would be when Mitt Romney was 31 years old)(He's lying, incidentally, in the following video about his dad marching with Martin Luther King

The earliest known recorded Mormon statement affirming black priesthood denial came about three years after Smith's death from Apostle Parley P Pratt on Apr 25 1847, following the departure from Nauvoo of those Saints following Brigham Young. According to Esplin, it "offhandedly referred to priesthood denial to the Blacks" -specifically prompted by the unauthorized practice of polygamy at Winter Quarters by one William McCary, a black Indian whom Pratt characterized as a "black man with the blood of Ham in hiim which lineage was cursed as regards to the priesthood".