In 1846, about 13,500 Mormon pioneers fled Nauvoo, Illinois, in search of religious freedom, departing in phases to prepare the way for those who would follow. Their journey began by crossing the Mississippi River and continued about 1,300 miles across Iowa into the western mountains. After a difficult trek, the first emigrants arrived in the Great Salt Lake Valley in 1847, and thousands more came later. Winter Quarters, about 305 miles from Nauvoo, sheltered trail travelers before they continued west, and several hundred people died there during the harsh winter of 1846-47. Chimney Rock, about 756 miles from Nauvoo, was a tall rock formation visible from a great distance where emigrants stopped to study and draw the geologic feature. About 1,300 miles from Nauvoo, This is the Place Heritage Park marks the area where Brigham Young first glimpsed the Great Salt Lake Valley and explores early European American settler life. The Nauvoo Temple was dedicated in May 1846 just before most Latter-day Saints left town; soon after, fire damaged the building, followed by a tornado two years later, and it was reconstructed in 2000. This was the largest planned migration in the United States, totaling nearly 70,000 by 1869, with later travelers beginning from other places over the next two decades.