Mountain Meadows, small valley in extreme SW Utah, where in 1857 a party of some 140 emigrants bound for California were massacred. It was a period when friction between Mormons and non-Mormons was acute, with Mormons bitterly resenting the coming of U.S. troops to enforce federal laws in their territory. Earlier that year a Mormon convocation had declared the independence of Utah from the United States, and Mormon hostility toward westward-bound travelers had escalated. In Sept., 1857, a party of emigrants from Arkansas, with a few from Missouri and Illinois, led by Charles Fancher, encamped at Mountain Meadows, a well-known camp site on the Spanish Trail. There they were attacked by a large band of Mormons, many disguised as members of the local Paiute tribe, allegedly accompanied by real Paiutes and apparently led by Mormon John D. Lee.

After three days (Sept. 8–11) of defending themselves behind their wagons, the emigrants were approached under a flag of truce by the Mormons, who offered to protect them in a retreat to Cedar City but instructed them to go unarmed and on foot, ostensibly to allay the suspicions of the Paiute. While following these instructions, the entire party, with the exception of 17 of the youngest children, were massacred. The Mormons were charged with inciting and directing the attack, and anti-Mormon feeling was intensified; Mormons attempted to blame the attack on the Paiutes. Several investigations were made, but it was not until 1874 that Lee, a fanatical Mormon and adopted son of Brigham Young, was arrested. In 1875, Lee and three associates accused of complicity were excommunicated. Lee was convicted of murder and in 1877 was put to death at the Mountain Meadows site. No other members of the raiding party were ever charged. Into the 1990s the Paiutes continued to be widely blamed for the massacre, which remains a controversial event in the history of the American West.

See studies by J. Brooks (2d ed. 1962, repr. 1970), W. Bagley (2002), S. Denton (2003), and R. W. Walker et al. (2011).