Why did Mormons emigrate to the area between the rocky mountains and great salt lake?

When the Church of Jesus Christ of Latter Day Saints (the Mormon religion) settled in Independence Missouri, their numbers started to outnumber non-mormon settlers. The governor of Missouri, Lilburn Boggs ordered an "extermination order" on the Mormons. The Order lead to the Haun's Mill massacre in which 240 men attacked the town. several Mormons who were wounded surrendured but were still shot to death. In the end, at least seventeen Mormons were killed with thirteen more injured. three of the 250 men who attacked were wounded (but not fatally). The Mormons were forced out of Missouri and went to Nauvoo Illinios. Soon, the Mormon population grew to a large number there too. In Nauvoo Illinois, the prophet Joesph Smith was arrested under false accusations and taken to Carthage Jail in Illinois. On June 27, 1844, a mob stormed the jail. Joesph Smith and his brother Hyrum Smith were killed. In October 1844, the town of Warsaw announce a "wolf hunt" (Mormons being the wolves to hunt). The Mormon leaders made a truce and the city of Nauvoo emptied of Mormon in 1446. In 1848, the Mormon temple was destroyed by arsonists. The new Mormon prophet had received revelation that Joesph Smith received from God that showed the valley of Salt Lake. So the Mormons moved West until they reached Salt Lake, although some did go to California.