The district was declared a National Historic Landmark in 1961.[2] It is significant as the headquarters of The Church of Jesus Christ of Latter-day Saints (LDS Church) from 1839 and 1846, and as an important early example of community planning by the LDS church. The city's basic plan is still discernible despite the many modern intrusions, and there are a wealth of historical archaeological sites related to the early LDS settlement period, including the site of the main temple, which occupied a prominent location in the city; it was burned in 1848 and its remains were levelled by a tornado in 1865. Due to the large influx of Mormons, Nauvoo became Illinois's largest city for a brief period in the 1840s.