Why did the Mormons leave?

Leave where? Mormons are still around and are growing rapidly. There are almost 14 million of them all around the world!

The Mormons under Brigham Young left their city of Nauvoo in 1846. His goal as was Joseph Smiths was to form a new Zion to the West.

One of the reasons for the persecution of the Mormons was their belief that God condoned polygamy.