He is the great-great-grandfather of Mitt Romney, the 2012 Republican candidate for President of the United States, and Jon Huntsman Jr., diplomat and former Governor of Utah, who served as the U.S.

The young couple migrated west, where they settled near Cleveland, Ohio, where Pratt purchased land and constructed a home.

In Ohio, Pratt became a member of the Reformed Baptist Society, also called "Disciples of Christ", influenced by the preaching of Sidney Rigdon.

While traveling to visit family in western New York, Pratt read a copy of the Book of Mormon owned by a Baptist deacon.

Continuing on to his family's home, he introduced his younger brother, Orson Pratt, to Mormonism and baptized him on September 19, 1830.

Arriving in Fayette, New York, in October 1830, Pratt met Joseph Smith and was asked to join a missionary group assigned to preach to the Native American tribes on the Missouri frontier.

Pratt became close friends with the Smiths, particularly Joseph, with whom he would later experience persecution and imprisonment, including incarceration at Liberty Jail.

[7] In February 1834, Pratt and Lyman Wight headed back to Kirtland to report on the events in Missouri to Joseph Smith.

[8] From Kirtland, Pratt traveled with Smith in Pennsylvania and western New York, preaching and trying to recruit people to serve in Zion's Camp.

Thankful had run up large debts in Pratt's absence, and when he returned with her to Ohio, some felt he was trying to flee his creditors and criticized him for it.

In addition to having converted his brother Orson and preacher Sidney Rigdon, Parley Pratt introduced the Mormon faith to several future church leaders, including Frederick G. Williams, John Taylor and his wife, Leonora, Isaac Morley, and Joseph Fielding, along with his sisters, Mary and Mercy.

In 1835, Pratt entered the leadership of the early Latter Day Saint movement when he was selected as one of the original Quorum of Twelve Apostles.

While presiding over the church's branches and interests in New England and the mid-Atlantic states, Pratt published a periodical entitled The Prophet from his headquarters in New York City.

[12] Other works by Pratt included Late Persecutions, Millennium and Other Poems, at least ten tracts published while he served as editor of the Millennial Star, and "Proclamation to the People of the Coasts and Islands of the Pacific", written by Pratt in the summer of 1851 in San Francisco, California, and published by W. C. Wandell in Sydney, Australia.

Pratt's writings also corroborate many events and revelations which are found in a book of Latter Day Saint scripture known as the Doctrine and Covenants.

[32] Fearing that Eleanor would abscond to Utah Territory with their children, Hector sent his sons and daughter to New Orleans, Louisiana, to live with their maternal grandparents.

For religious and cultural reasons, Eleanor considered herself unmarried at the time of her sealing to Pratt, but she had not legally divorced from Hector.

[42] Shortly after being secretly released, on May 13, 1857, Pratt was shot and stabbed by Hector on a farm northeast of Van Buren, Arkansas.

Some writers have viewed Pratt's death as the act of a jealous husband, deeply angered by a man who had "run off" with his wife.

[43] A 2008 Provo Daily Herald newspaper article characterized McLean as a man who had "hunted down" Pratt in retribution for "ruining his marriage".

"[46][47] A 2007 article in the Deseret Morning News said that "Pratt was killed near Van Buren, Ark., in May 1857, by a small Arkansas band antagonistic toward his teachings".

[48] The historian Will Bagley reports that McLean and two friends tracked Pratt after he was released by Van Buren's magistrate.

[50] Due to Pratt's personal popularity and his position in the Quorum of the Twelve, his murder was a significant blow to the Latter-day Saint community in the Rocky Mountains.

[52] After the massacre, some Mormons circulated rumors that one or more members of the party had murdered Pratt,[53] poisoned creek water that subsequently sickened Paiute children,[54] and allowed their cattle to graze on private property.

[61] Mary Ann was a native of Bethel, Maine (part of Massachusetts until 1820) whose first relative to join the church was Patty Bartlett Sessions, later a prominent midwife in Utah.

[61] Mary Ann and Pratt at times demonstrated a deep companionship in their marriage, most fully shown by her joining her husband in prison in Missouri.

Pratt made several attempts to get Mary Ann to join him in traveling west in 1846 and 1847, but after spending the winter of 1846–47 in an abandoned Nauvoo, she chose to return to Maine.

She worked as a midwife, remained in the LDS Church, and became a leading advocate for Mormon women against the attacks of those opposed to polygamy.

After he started practicing plural marriage, the longest period of time he had with his family were the 18 months following his return from a mission to Chile.

[72] One of Pratt's great-great-great-grandsons is Jon Huntsman, the former Utah governor and Ambassador to China, and an unsuccessful candidate for the 2012 Republican presidential nomination.