John Charles Fremont conducted five expeditions to the West during a period of twelve years (1842-1854). On four occasions, during three of these expeditions (1843-1844, 1845, and 1854), the explorer entered the Utah region. His explorations in northern Utah in 1843 focused primarily on the scientific analysis and survey of the Great Salt Lake. In 1844, Fremont again entered the Utah area and made scientific observations and calculations about the region, including accurately defining the geographic region known as the Great Basin, the name given it by Fremont. In 1845, Fremont proceeded through Utah while enroute to California and spent a considerable amount of time in the Utah area, once again making significant observations. Finally, during the winter of 1854, the explorer surveyed portions of central and southern Utah with intentions of locating a suitable transcontinental railroad route. In this thesis, each of these expeditions is discussed in detail and summaries given concerning the implications each had on the history of the state.