The future Salt Lake County area was settled by European Americans in 1847 when Mormon pioneers of The Church of Jesus Christ of Latter-day Saints fled religious persecution in the East. They arrived in the Salt Lake Valley after descending what settlers later called Emigration Canyon. Brigham Young, their leader, declared "This is the place" after seeing the valley. Compared to eastern regions, it seemed arid and unpromising to some of the migrants. Settlers used extensive irrigation to develop agriculture and the flourishing, self-sufficient city, known then as Great Salt Lake City. Thousands of Mormons joined them in the next several decades.