Joseph Smith was given a hearty welcome by the Saints in Far West, Missouri, who were pleased to have the prophet living among them. Smith's first order of business in Missouri was to cleanse the Church by excommunicating 50 of the leading apostates. Although it pained their hearts to do so, Church leaders also found it necessary to excommunicate Oliver Cowdery and David Whitmer, two of the first witnesses of the gold plates.
The Church’s historian was among those excommunicated, and he refused a request to hand over his historical notes to the Church. Therefore, in April of 1838, Joseph Smith and Sidney Rigdon set about writing their own account of Smith's life and the early events of the Restoration of the Church in the latter-days, some of which was later added to the collection of holy scripture known as The Pearl of Great Price.
In May, the prophet went out to choose areas of land in northern Missouri for the Saints emigrating from Ohio to settle. While at a certain spot along the Grand River, Smith received a revelation from Jesus that this was the site of Adam-ondi-Ahman, the place Adam and Eve had lived after being expelled from the Garden of Eden. This news was met with joy by the incoming Saints who poured into the area, considering it a blessing to live where Adam had once dwelt.
The harsh criticism the prophet endured in Ohio had spread to a lesser degree among the Saints in Missouri, and some excommunicated former Church leaders continued to harass Joseph Smith with lawsuits. In response, an angered Sidney Rigdon publicly spoke out against the prophet's dissenters, calling them "good for nothing, but to be cast out, and to be trodden under foot of men.”
A threatening letter was signed by 84 members of the Church and issued to the dissenters. And Joseph Smith approved the formation of the Danites—a paramilitary group oath-bound to avenge the Church's enemies by lying, robbing, and murder when necessary. This letter, together with intimidation from the Danites, successfully frightened away the dissenters, but damaged the public reputation of the Church, and furthered a growing anti-Mormon sentiment in northern Missouri.
Relations between Missourians and Mormons got worse weeks later when Rigdon made another fiery public address threatening that if mobs sought to harm the Saints, "It shall be between us and them a war of extermination, for we will follow them, till the last drop of their blood is spilled, or else they will have to exterminate us." Copies of the speech were circulated, and were considered by Missouri officials sufficient to bring changes of treason.
Violence broke out on election day in early August of 1838, when unarmed Mormons went to vote but were met at the polls by a mob that was riled up by a man named William Peniston who was heard to say, "The Mormon leaders are a set of horse thieves, liars, counterfeiters, and you know they profess to heal the sick, and cast out devils, and you all know that is a lie."
A punch was thrown by the mob bully Dick Welding, and fisticuffs between the two groups ensued. One of the Saints took a stake from a woodpile and began striking the Missourians with great strength. Additional makeshift weapons were used in the melee, and several on both sides were seriously injured.