Utahs Timeline By Hanna Bieber Jul 24, 1847 Brigham Young and Mormon pioneers arrived in Salt Lake Valley Sep 11, 1857 Mountain Meadows Massacre May 10, 1869 First Transcontinental Railroad Jan 4, 1896 Utah became 45th state May 22, 1910 earthquake in salt lake Oct 13, 1920 Loraine Day was born in rosevelt utah Nov 13, 1937 Antoine Robidoux builds a trading post in the Uintah Basin. Aug 11, 1999 Tornado hit salt lake