Why did the Mormons settle in Utah?

The Mormons went to Utah to escape persecution and death at the hands of the mobs that had driven them out of other states.

In the early days of the Church there was a lot of prejudice against its members, and as result of the prejudice the early church members were chased out of one place after another. They had moved between New York, Illinois, Missouri ,and Ohio, and in Missouri the state actually passed a law making it legal to kill a member of the Church of Jesus Christ of Latter-day Saints. This Law stayed on the books until 1976.

The United States Government in response to the petitions of the Church members for help, effectively told them to get out of the country. So they sought an area that was far from other people.

The reason the Mormons left was because they had been kicked out of Ohio, Missouri, and Illinois. They appealed to the federal government for assistance, but were told that the government could do nothing for them. So, they went where they knew they could practice their religion in peace - a land that was rumored to be uninhabitable - the valley of the Great Salt Lake.