Utah History By hipo Feb 4, 1846 The first Mormons left Nauvoo Apr 12, 1853 John C. Fremont began his expedition to Colorado Mountains and Utah in search of a railroad route over the Central Rockies. Jul 1, 1862 The US Congress outlawed polygamy for the 1st time May 10, 1869 The Transcontinental Railroad was completed Aug 16, 1880 David King Udall was called to be the Mormon bishop in St. Johns Sep 24, 1890 The Manofesto was written May 1, 1900 The Scofield Mine Disaster May 26, 1910 Utah's State Capital was built Oct 29, 1929 When the Great depression started to start Dec 5, 1933 Ends Prohibition