When the Mormon pioneers moving westward across the Great Plains began settling the Salt Lake Valley around the Great Salt Lake in 1847 and for many years afterward, they relied on existing institutions within the Church of Jesus Christ of Latter-day Saints (LDS Church) or the secular civil governments.

[5] The creation of the Territory with no mention at all of the divisive issue of slavery in the documents, was partially the result of a petition sent by the Mormon pioneers under the leadership of Brigham Young (1801–1877, served 1847–1877), the second church president.

The Mormon settlers had drafted a state constitution in 1849 and Deseret had become the de facto government in the Great Basin by the time of the creation of the subsequent Federal Utah Territory.

The first Territorial Capital City and Capitol building was located 1850 to 1856 in the small town of Fillmore, Utah, named for the new 13th President Millard Fillmore, who approved and signed the Congressional organic act and territorial erection bill of September 1850, and the small local government was set up here including the meetings of the Territorial Assembly, although first governor and second LDS Church president Brigham Young remained mostly in his Beehive House (current historic site) residence in Salt Lake City, but traveling to Fillmore 1850 to 1856, until his death in 1877.

A massive monumental Utah State Capitol building with landmark dome was later constructed there on the scenic ridge overlooking from the slopes of the surrounding Wasatch Range mountains to the present.

[7] Mormon governance in the territory was regarded as controversial by much of the rest of the nation, partly fed by continuing lurid newspaper depictions of the polygamy marriage practiced by the settlers, which itself had been part of the cause of their flight from their previous homes and center back East in Nauvoo, Illinois, in the United States, trekking westward across the continent to the Great Salt Lake basin after being persecuted and forcibly removed from their settlements in several Eastern states.

Although the Mormons were now the majority in the Great Salt Lake basin, the western area of the new territory soon began to attract many non-Mormon settlers, especially after the discovery of silver at the famous Comstock Lode ore deposits in the Virginia City area, east of the Sierra Nevada mountain ranges and Lake Tahoe (of present-day western Nevada) in 1858.

Only three years later on the eve of the outbreak of the American Civil War in 1861, and partly as a result of this, with its importance of the recovered silver bullion for Federal Treasury coffers plus huge growth in population with the influx of prospecting miners (and assorted supporting commercial business interests) and with the subsequent intensive deep shaft industrial mining and drilling, the new Nevada Territory was then created out of the western part of the previous Utah Territory of a decade before.