In 1856, the newly-formed Republican Party announced its platform opposing “the twin relics of barbarism—polygamy and slavery.” President James Buchanan, perhaps in an attempt to distract from the growing threat of Southern secession, determined to address the “Mormon problem” by marching 2,500 U.S. troops to Utah in early 1857, tasked with installing a federally-appointed governor and building a military fort to temper the unruly Mormon kingdom. News of this reached Brigham Young, who saw the advance as a hostile takeover. The Nauvoo Legion was called back into service and militamen began drilling for a likely war against the U.S. Army. Following the May, 1857, murder of Mormon apostle Parley P. Pratt in Arkansas, anti-outsider rhetoric reached fever pitch, fomenting into what is widely considered the darkest day in Mormon history: the September 11, 1857 massacre of a migrant party of 116 men, women, and children, slaughtered by a Mormon militia at Mountain Meadows in Southern Utah. Historical consensus maintains that orders to kill the passing wagon party came from local militia leaders, although some speculate that the orders came from Brigham Young. While evidence linking Young directly to the massacre is weak, there is little doubt that the zealous rhetoric he encouraged had fanned the flames of fanaticism, adding religious violence in Utah to violence provoked over sovereign rights in “Bleeding Kansas” and other Western territories during the same period. Following the massacre, an attempt to cover up the slaughter by blaming Paiute Indians became the official explanation. Only one Mormon, John D. Lee, was convicted for involvement. Lee was executed by firing squad twenty years after the massacre.
Gospel Topics essay: “Peace and Violence among 19th-Century Latter-day Saints” (Read from the section titled “Violence in Utah Territory” to the end of the article).