The founding of Nauvoo transformed a nearly empty, swampy bend of the Mississippi River into a thriving city and the center of an ambitious Mormon theocracy. Under Joseph Smith, the settlement acquired unusual civic powers, developed a disciplined militia, and became the setting for major theological innovations. Its rapid rise also concentrated religious, political, and military authority in one place, leaving a legacy that extended beyond the city’s founding and its later abandonment.

Site and settlement

About a month after breaking out of jail in Missouri, Joseph Smith surveyed the eastern bank of the Mississippi at Hancock County, Illinois, and chose the site for a capital of the Kingdom of God on earth. The low promontory was then a malarial swamp, so wet that foot travel was difficult and ox teams could not pass. Its advantages were practical: the land was almost uninhabited, and its owner was willing to sell acreage to the Saints on credit.

The settlers began building with characteristic industry. Within five years, more than fifteen thousand people lived in and around Nauvoo—about ten times its present-day population at the time of the book’s account. It became the second-largest municipality in Illinois, a city created from almost nothing that rivaled Chicago. The speed and scale of the transformation established Nauvoo not merely as a refuge after expulsion, but as a visible demonstration of the community’s capacity to organize and build.

Charter and concentrated authority

Nauvoo’s political character was shaped by a highly unusual charter that the Illinois General Assembly passed in December 1840. Illinois was eager to attract industrious settlers, and sympathy for the Latter-day Saints remained strong after their expulsion from Missouri. The charter granted the city sovereign rights and powers exceptional in Illinois and across the nation. The unintended result was to make Joseph, as the city’s head, the effective ruler of an autonomous city-state.

Joseph’s authority was not only civic or religious. He commanded the Nauvoo Legion, a well-armed and rigorously disciplined militia said to number nearly half as many men as the entire American Army at the time. Seeking a still larger force, he petitioned Congress to authorize a one-hundred-thousand-man army under his personal control; Congress declined. The scale of the request nevertheless shows how the city’s special political standing encouraged ambitions that reached far beyond its borders.

In January 1844, Joseph announced his candidacy for president of the United States. He treated the campaign seriously, sending 586 missionaries—including ten members of the Quorum of the Twelve Apostles—to all twenty-six states and Wisconsin Territory to seek support. Nauvoo thus served as more than a local seat of power: it became the launching point for an effort to extend Joseph’s influence nationally.

Religious innovation and concealed practice

Nauvoo was also the setting for a concentrated period of theological development. Joseph introduced vicarious baptism for the dead, allowing living members to be baptized on behalf of deceased ancestors. He established the temple endowment ceremony and taught that God had once been a man and that human beings could become gods. These teachings expanded the religious system being built around the city and gave its temple-centered life an increasingly distinctive form.

Plural marriage occupied a different and more guarded place in this period. Joseph had continued taking plural wives in Ohio and Missouri, and did so more frequently in Nauvoo in the early 1840s, while concealing the practice from non-Mormons and all but a select circle of followers. On July 12, 1843, he formally codified the principle in a revelation. Unlike the other theological developments described alongside it, the revelation remained secret and was not acknowledged until 1852, eight years after his death. Nauvoo’s religious history therefore joined public doctrinal innovation to a private practice that leaders withheld from most of the community and the outside world.

Departure and institutional legacy

The settlement’s growth did not prevent the Saints from leaving it. In February 1846, the first wagon trains departed Nauvoo amid violence and pressure in Illinois. At Sugar Creek, Iowa, where the emigrants regrouped before continuing west, church leaders openly shared the previously concealed doctrine of plural marriage with the rank and file. The disclosure marked a change in what members were told as the community moved out of the city and toward the Rocky Mountains.

The hardships of the exodus, following violence in Missouri and Illinois, strengthened the commitment of those who completed the journey. The survivors formed a close-knit community whose loyalty to Brigham Young was described as unconditional. After Joseph’s murder and the acquittal of the men tried for it, Brigham called for God and the Saints to avenge the blood of church leaders; church authorities made an Oath of Vengeance part of the temple endowment ceremony. Nauvoo’s founding had gathered civic, military, and religious power in one place. Its later dispersal did not erase that institutional inheritance: the community carried its doctrines, rituals, and leadership structures westward.