In Missouri and Illinois , animosity between the Mormon settlers and locals grew , which would mirror those in other states such as Utah years later . Violence finally erupted on October 24 , 1838 , when militias from both sides clashed and a mass killing of Mormons in Livingston County occurred 6 days later . An executive order was filed during these conflicts , and the Mormons were forced to scatter . Brigham Young , seeking to leave American jurisdiction to escape religious persecution in Illinois and Missouri , led the Mormons to the valley of the Great Salt Lake , owned at the time by Mexico but not controlled by them . A hundred rural Mormon settlements sprang up in what Young called " Deseret " , which he ruled as a theocracy . It later became Utah Territory . Young 's Salt Lake City settlement served as the hub of their network , which reached into neighboring territories as well . The communalism and advanced farming practices of the Mormons enabled them to succeed . They sold goods to wagon trains passing through and came to terms with local Indian tribes because Young decided it was cheaper to feed the Indians than fight them . Education became a high priority to protect the beleaguered group , reduce heresy and maintain group solidarity
mass killing
Haun's Mill massacre
American frontier