"The best organized mass migration in American history" began in 1846 as the first group of Mormons, led by Brigham Young, traveled from Nauvoo, Illinois to Great Salt Lake in Utah. Through 1869, more than 70,000 Mormons headed west along the 1,300-mile Mormon Pioneer Trail.
The Mormons followed existing trails and used maps and accounts from previous explorers to plan their route west. Traveling in military-style "companies," they made improvements to the trail and built support facilities to aid those following. They also developed the use of handcarts, fashioned a basic odometer and built the first commercial ferry (a replica of which can be seen at the Fort Casper Museum, on the site of a Wyoming crossing that proved critical to the trail).