In 1844, reeling from the murder of their founder and prophet, Joseph Smith, and facing continued mob violence in their settlement in Illinois, thousands of Latter Day Saints (better known as Mormons) threw their support behind a new leader, Brigham Young. Two years later, Young led the Mormons on their great trek westward through the wilderness some 1,300 miles to the Rocky Mountains—a rite of passage they saw as necessary in order to find their promised land.

Young, and 148 Mormons, crossed into the Great Salt Lake Valley on July 24, 1847. For the next two decades, wagon trains bearing thousands of Mormon immigrants followed Young’s westward trail. By 1896, when Utah was granted statehood, the church had more than 250,000 members, most living in Utah. Today, according to official LDS statistics, Utah is home to more than 2 million Mormons, or about one-third of the total number of Mormons in the United States.

Forced to flee anti-Mormon hostility in New York, Ohio and Missouri, in 1839 Smith and other church members arrived in Nauvoo, Illinois, on the banks of the Mississippi River. Jailed in Missouri, Smith was allowed to escape to Illinois, where he helped build Nauvoo into a thriving city. Then in mid-1843, after Missouri’s governor blamed a failed assassination attempt on Mormon agitators, the governor of Illinois, Thomas Ford, agreed to extradite Smith to face trial.

Why all the hostility against Smith and his fellow Mormons? “The Mormons were fairly clannish, you might say,” Matthew Bowman, professor of history at Henderson State University and author of The Mormon People: The Making of an American Faith, explains. “They tended to vote in blocs, they tended to consolidate all their economic activity within their own communities. These kinds of things generated suspicion from people around them.”

Smith evaded extradition for a while, and even began planning a run for president of the United States in 1844. But when a local newspaper, the Nauvoo Expositor, published a front page article criticizing the Mormon doctrine of polygamy, Smith ordered its printing press smashed. In the ensuing uproar, Smith was convinced to turn himself in at the county seat in Carthage to face a hearing.

On June 27, 1844, a mob gathered at the jail and killed Smith and his brother Hyrum. Though the Mormons had been considering migrating West, beyond the reach of the United States government, before their founder’s murder, the crime solidified this intention. And Brigham Young, who emerged as de facto leader after Smith’s death, had just the place in mind.

Young and his fellow apostles considered options such as Texas (during its brief period as an independent republic), California and Canada. But relying on the reports of Western explorers like John C. Frémont, they decided on the Great Salt Lake Valley in the Rocky Mountains. At the time, the region was part of Mexico, with limited oversight by the Mexican government. They set out from Nauvoo in April 1846, but were forced to spend several months camped along the Missouri River between Iowa and Nebraska. When spring came, Young and an advance group of 143 men, three women and two children left the winter camp and headed for their final destination.

Despite warnings about the region’s unsuitability for agriculture and the hostile Native Americans living near the smaller, freshwater Utah Lake, the Mormons were drawn to the low population of the Salt Lake Valley. And the mountains ringing the valley were stocked with freshwater streams and creeks that could nourish crops, despite the saltiness of the Great Salt Lake itself. “It didn’t seem to be wanted by any other white people,” Bowman says of Young’s chosen spot. “There was not a large Native American presence, but there was the potential for agriculture, and for supporting a large population.”

In a later account of their arrival, the future LDS leader Wilford Woodruff wrote that Young paused and gazed down at the valley for several minutes when they first arrived, and “he saw the future glory of Zion and of Israel, as they would be, planted in the valleys of these mountains.”

When Young and his followers first arrived in the Great Salt Lake, the region was still part of Mexican territory. But in early 1848, Mexico ceded some 525,000 square miles of its territory to the United States at the end of the Mexican-American War, including all or parts of present-day Arizona, California, Colorado, New Mexico, Wyoming—and Utah.

Young saw an opportunity in this turn of events: State governments had a lot of power, and controlling one could give the Mormons considerable autonomy. In 1849, he sent representatives to Congress with a proposed map of the state of Deseret (a word from the Book of Mormon meaning “honeybee”.) The state would have been massive, encompassing present-day Utah, most of Nevada, good chunks of Colorado, Arizona, New Mexico and Idaho, and even the city of San Diego.

Instead, as part of the Compromise of 1850, Congress greatly reduced Deseret’s size and renamed it the Utah Territory. President Millard Fillmore appointed Young as territorial governor, a decision made “largely as a matter of practicality,” Bowman points out, as Young had essentially been governing Deseret (as he called it) and the Mormon Church as one entity for three years already.

Young largely ignored the federal agents the Fillmore administration sent to Utah, and did what he wanted. Federal courtrooms sat empty, while Mormon leaders filled the territorial legislature. Suspicions of theocracy, and particularly of the Mormon practice of polygamy, which the church made public in 1852, “really inflamed the animus of Americans—particularly Protestants—against the Mormons,” Bowman says. It also made the Mormons a useful political foil for Washington politicians, some of whom likened the religion to another highly divisive institution: slavery.

In 1857, President James Buchanan declared the Utah Territory to be in rebellion, and ordered federal troops to Salt Lake City to force Young to step down in favor of a non-Mormon governor. Though Young eventually agreed to be replaced as territorial governor, the Mormon practice of plural marriage would delay Utah’s statehood for nearly four more decades.

Congress began passing laws trying to get rid of polygamy (or bigamy, as it was then called) in the early 1860s. Though during the Civil War these laws were not pursued, Bowman says, this changed in the decade after that conflict. In the 1874 case Reynolds v. United States, in which Young’s secretary, George Reynolds, tested the constitutionality of an 1862 anti-bigamy law, the Supreme Court ruled unanimously that the Constitution does not protect polygamy.

In the 1880s and early 1890s, more than 1,000 Mormon men would be convicted of charges relating to plural marriage. In 1887, the Edmunds-Tucker Act took square aim at the Mormon church itself, disincorporating it and authorizing the federal government to seize much of its property. Again the Mormons brought suit, but in 1890 the Supreme Court ruled the Edmunds-Tucker Act constitutional. “When that happens, the president of the church, Wilford Woodruff, issues what Mormons call the Manifesto,” Bowman explains. “It’s a proclamation saying that for the good of the church, for the survival of the church, we have to abandon plural marriage.”

Once Woodruff had formally renounced polygamy on behalf of the LDS, Congress’ attitude changed greatly, and the path to statehood became considerably clearer. On January 4, 1896, Utah became a state. A year later, when the church celebrated the 50th anniversary of Brigham Young’s arrival in the Salt Lake Valley—Young himself died in 1877—the newly completed Mormon temple in Salt Lake City was draped in American flags.

Utah is now home to more than 2 million Mormons, or about one-third of the total number of Mormons in the United States.