A map of Utah Territory, probably 1870s or 1880s.
The people who settled in Salt Lake Valley were disappointed when Congress chose not to make Utah a State right away, but instead made it a Territory of the United States. Learn more about why.
In a Territory, the people didn't get to vote for their own governor and many other officials. Instead, the President of the United States appointed them. (Who were these Territorial governors?)
Utah stayed a Territory for a long time, mostly because the Mormons did not want to give up polygamy--and most national politicians did not want Utah to be a state unless they did give it up. (They gave it up in 1890.) It wasn't until 1896 that Utah became a state.
In 1850, Americans were fighting bitterly (mostly with words) over slavery. Northerners wanted slavery to go away, and Southerners wanted slavery to stay legal. Northerners wanted every new state to be a "free" state, but Southerners wanted new states to be "slave" states.
The Compromise of 1850 admitted California into the Union as a "free" state. At the same time, it created New Mexico Territory and Utah Territory, and gave the citizens of each territory the responsibility to decide for themselves whether to allow slavery or not. Congress also chose the name "Utah" for the territory, not "Deseret," as the people living in the territory wanted.
In the Compromise of 1850, both the North and the South got some of what they wanted and didn't get other things they wanted.
It was the same for the people living in the new Utah Territory. They didn't get statehood right away, and they lost some independence, but they did become an official political part of the United States ... and eventually they would become a state.