Nauvoo is a small city in Hancock County, Illinois, United States, on the Mississippi River near Fort Madison, Iowa. The population of Nauvoo was 950 at the 2020 census. Nauvoo attracts visitors for its historic importance and its religious significance to members of The Church of Jesus Christ of Latter-day Saints, Community of Christ, and other groups stemming from the Latter Day Saint movement, as well as the Icarians. The city and its immediate surrounding area are listed on the National Register of Historic Places as the Nauvoo Historic District.