Thirty thousand Mormons Lived in Western Illinois in the 1840’s, with only about half of them living in Nauvoo. Almost all discussion concerning Mormons between 1839 and 1846 is limited to Nauvoo. Researchers are lucky to find a handful of brief articles about Mormons outside the city. Upon further investigation, these settlements emerge as being far more important to the success of Nauvoo than this neglect indicates.
Ultimately, most settlements resulted from three causes: Mormon interaction and experience with Illinois before their expulsion from Missouri, overwhelming economic need, and proselyting successes. In many of their actions, church leaders assumed a reactive role in responding to these circumstances.
Reynolds, R Philip, "Spiritual Economics: Some Financial Considerations of Mormon Settlement in Illinois" (2007). Library Faculty and Staff Publications. 14.