Members of the Church of Jesus Christ of Latter-day Saints (also known as Mormons), stoked by religious zeal and a deep resentment of decades of public abuse and federal interference, murder 120 emigrants at Mountain Meadows, Utah on September 11, 1857.

Although historical accounts differ, the conflict with the wagon train of emigrants from Missouri and Arkansas apparently began when the Latter-day Saints refused to sell the train any supplies. Some of the emigrants then began to commit minor depredations against fields, abuse the local Paiute tribes, and taunt the Mormons with reminders of how the Missourians had attacked and chased them out of that state during the 1830s.

Angered by the emigrants’ abuse and fired by a zealous passion against the growing tide of invading gentiles, a group of LDS guerillas from around Cedar City decided to take revenge. Cooperating with a group of Paiutes who had already attacked the train on their own initiative, the guerillas initially pretended to be protectors. The guerillas persuaded the emigrants that they had convinced the Paitues to let them go if they would surrender their arms and allow the Latter-day Saints to escort the wagon train through the territory. But as the train again moved forward under the LDS escort, a guerilla leader gave a pre-arranged signal. The Latter-day Saints opened fire on the unarmed male emigrants, while the Paiutes reportedly murdered the women.

Later accounts suggested that some Latter-day Saints had only fired in the air while others killed as few of the emigrants as they could. But when the shooting stopped in Mountain Meadows, 120 men and women were dead. Only 18 small children were spared.

As a direct result of the Mountain Meadows Massacre, the U.S. government demanded a new settlement from Brigham Young. In 1858, the Latter-day Saints agreed to accept a continued presence of federal troops and a Gentile governor for Utah Territory. No further significant LDS-Gentile violence occurred, and the Latter-day Saints were thereafter largely left to govern themselves. But the era of complete LDS domination of Utah ended as a result of the tragedy that day in Mountain Meadows.