Smith was a prominent leader in the settlement of many communities in southern Utah, and played a role in the chain of events preceding the Mountain Meadows Massacre on September 11, 1857.

Smith served as a missionary to the eastern United States, traveling and preaching during the summers of 1835, 1836, and 1837, while attending school each winter.

The two men replaced former apostles Thomas B. Marsh, who had left the church, and Orson Hyde, who had been disfellowshipped and removed from his position.

Under direction from the General Assembly of the State of Deseret, the group organized the political entity of Iron County and elected Smith as chief justice.

During the winter of 1850–51, the settlers constructed a fort enclosing homes, a meeting house, a school, and a watch tower.

Scholars have asserted that Smith's tour, speeches, and personal actions contributed to the fear and tension in these communities, and influenced the decision to attack and destroy the Baker–Fancher emigrant train near Mountain Meadows, Utah.

Although Smith's rank in the Legion was simply a private,[11] one Parowan resident understood that part of the purpose of his trip was to represent the church leadership and to organize the regiment, inspect the troops, and provide instructions.

[12] During the tour, Smith gave military speeches[13] and counseled Mormons that they should prepare to "touch fire to their homes, and hide themselves in the mountains, and to defend their country to the very last extremity."

"[18] Isaac C. Haight, Cedar City stake president, and second in military command under Dame, met with Smith again on August 21.

[20] Smith later said he was uncomfortable, perhaps "on account of my extreme timidity", because some of the militia members were eager that "their enemies might come and give them a chance to fight and take vengeance for the cruelties that had been inflicted upon us in the States", such as the Haun's Mill massacre,[21] where 18 Mormons were killed in 1838 in a skirmish with the Missouri militia during the Mormon War.

On the way back to Salt Lake City, Smith was accompanied by a party including Jacob Hamblin of Santa Clara, a newly appointed Mormon missionary to the Natives in the region who also ran a federally funded "Indian farm" next to Mountain Meadows.

[24] When the Baker–Fancher party inquired about places to stop for water and grazing, Hamblin directed them to Mountain Meadows,[25] near the "Indian farm" there, a regular stopover on the Old Spanish Trail.