The Mormon Trail traces the route by which members of The Church of Jesus Christ of Latter-day Saints left Nauvoo, Illinois, beginning in February 1846, after mounting hostility culminating in the 1844 murder of founder Joseph Smith forced the church's abandonment of the city it had built on the Mississippi River. Brigham Young, who had assumed leadership of the majority of the movement's members, organized the migration in companies that crossed Iowa through the winter and spring of 1846, wintered at way stations including Winter Quarters near present-day Omaha, Nebraska, and pushed west along the north side of the Platte River, deliberately avoiding the established Oregon Trail on the river's south bank to reduce friction with other westbound traffic. The vanguard company, led by Young himself, reached the Salt Lake Valley in July 1847, and Young's declaration on first seeing it, that this was the right place, became a foundational moment in Latter-day Saint memory of the trek.
Roughly seventy thousand Latter-day Saints are estimated to have traveled some version of the route between 1846 and 1869, most by wagon company but a distinctive minority, beginning in 1856, pulling their belongings in hand-drawn carts organized by the church as a cheaper alternative for poorer converts, chiefly recent immigrants from Britain and Scandinavia. Two of these handcart companies, the Willie and Martin companies, were caught by early snow in Wyoming in October 1856 with several hundred deaths among their members, a disaster that became, alongside the successful arrival of most companies, part of the trail's remembered history within the tradition.