From 1847 to the 1860s, the Mormon migration along the Great Platte River Road formed a distinctive chapter in westward expansion as the organized movement of an entire people seeking refuge in the mountains of the far west rather than the more random migration of individual families or companies to California or Oregon. Seeking to escape religious persecution in the east, the pioneer Mormon company traveled the Great Platte River Road in the spring and summer of 1847 and deliberately stayed on the north side of the Platte instead of using the more heavily traveled Oregon Trail on the south side. On July 24, 1847, Brigham Young's pioneer party founded Salt Lake City, which drew an estimated 60,000 Latter-day Saints to Utah along the Platte River Road over the next 20 years. Advance parties left messages on buffalo skulls for those who followed, and some companies were so poor that they pulled crude handcarts the 2,000 miles to Salt Lake City. Winter Quarters, near present-day Florence, Nebraska, became the chief outfitting point for the trek west, but during the winter of 1846-1847 more than 600 Mormons died there from disease and exposure. Organized in 1830 in upper New York State by Joseph Smith, the Church of Jesus Christ of Latter-day Saints later built Nauvoo, Illinois, before mobs expelled its members in 1845 and 1846. After Joseph Smith's death in 1844, Brigham Young became the Mormon leader and directed the exodus to Utah. More than 2,000 Mormons died along the trail, and Rebecca Winters' grave near modern Scottsbluff is one of the few preserved and marked graves.