Joseph Walker, who is working on the Joseph Smith papers, said documents show the Extermination Order of 1838 -- aimed at the Church of Jesus Christ of the Latter-Day Saints -- was timed to prevent Mormons from buying land they had improved, Mormon Times reported.
Local laws allowed what was known as pre-emption, Walker says. Settlers had the right to buy government land they had lived on and farmed, but if they were unable to do so, others could buy the improved land at the price of vacant land.
Mormons settled in Missouri in the early 1830s. They were driven out in 1838 by government-sanctioned violence, Walker said, and moved to Nauvoo, Ill., where Joseph Smith, the church's founder, was killed by a mob in 1844.
Brigham Young, Smith's successor, led the Mormons to Salt Lake City.