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The Nauvoo Legion: How a Religious City Built Its Own Army

A look at the state-sanctioned militia formed by Latter-day Saints in Nauvoo, Illinois, and its role in 19th-century American history.

By Garret Merkley · Explainer · Jun 11, 2026
Branched from The Missouri Extermination Order: Why Mormons Were Driven Out in 1838
Quick take
  • The Nauvoo Legion was a large, state-sanctioned militia formed by Latter-day Saints in Nauvoo, Illinois, in the 1840s.
  • Led by Joseph Smith, its purpose was to defend the city and its residents after previous persecutions.
  • Though legal under Illinois law, its size and the religious leadership of its officers created significant tension with neighboring communities.
  • The Legion's existence contributed to the escalating conflicts that ultimately led to the Saints' exodus from Illinois.

The Nauvoo Legion was a state-sanctioned militia established by members of The Church of Jesus Christ of Latter-day Saints in Nauvoo, Illinois, during the 1840s. It served as the primary defense force for the burgeoning religious city, reflecting a period when local militias were common in the American frontier, but its unique composition and scale made it a flashpoint for conflict.

A Legal Foundation for Self-Defense

After being driven from Missouri under an extermination order, the Latter-day Saints sought refuge in Illinois. In 1840, the Illinois legislature granted Nauvoo a city charter, which included a provision allowing the city to raise its own militia, known as the Nauvoo Legion. This was not unusual; many cities and counties at the time had the right to form local militias for self-defense and to maintain order. The charter granted broad powers, allowing the Legion to organize, drill, and perform military duties.

Structure and Scale of the Legion

The Nauvoo Legion was structured much like a regular army, with companies, regiments, and brigades. Its ranks were filled by Latter-day Saint men, and uniquely, many of its officers were also prominent religious leaders. Joseph Smith, the founder of the Church, was appointed Lieutenant General by the governor of Illinois, making him the highest-ranking officer. Under his leadership, the Legion grew rapidly. At its peak, it numbered several thousand men, reportedly rivaling the size of the entire standing U.S. Army at the time. This massive scale, combined with its distinctive uniforms and public drills, made it a highly visible and formidable force.

A Formidable Force
  • At its peak, the Nauvoo Legion reportedly numbered between 2,000 and 5,000 men.
  • Joseph Smith held the rank of Lieutenant General, a position granted by the state of Illinois.
  • The Legion engaged in regular drills and parades, showcasing its strength and organization.

Why the Legion Mattered

The Nauvoo Legion emerged from a desperate need for security and self-preservation. Having faced violent expulsions and persecution in Missouri, the Latter-day Saints viewed the Legion as essential for protecting their community, property, and religious freedom. It provided a sense of safety and autonomy in a time when state and federal protection often felt distant or inadequate. However, the Legion's very existence, particularly its size and the fusion of military and religious leadership, became a major source of concern and fear for non-Mormon neighbors. They saw it not just as a local militia but as a private army loyal only to Joseph Smith, potentially threatening the sovereignty of Illinois. This perception fueled deep mistrust, exacerbated existing religious and political tensions, and ultimately contributed to the escalating conflicts that culminated in Joseph Smith's assassination and the eventual exodus of the Latter-day Saints from Nauvoo.

Was the Nauvoo Legion legal?
Yes, the Nauvoo Legion was legally established under the provisions of the Nauvoo city charter, which was granted by the Illinois state legislature in 1840. State law at the time allowed for the creation of local militias.
How large was the Nauvoo Legion?
At its peak, the Nauvoo Legion numbered several thousand men, with estimates ranging from 2,000 to 5,000. This made it one of the largest, if not the largest, organized militia in the United States at the time.
Did the Nauvoo Legion fight in any battles?
While the Nauvoo Legion engaged in drills, parades, and maintained order within Nauvoo, it did not participate in any major military battles against external forces. Its primary role was defensive and as a local police force, though its presence was a constant factor in the tensions with surrounding communities.
What happened to the Nauvoo Legion?
After Joseph Smith's death in 1844, the Nauvoo Legion's legal standing became increasingly precarious. In 1845, the Illinois legislature repealed the Nauvoo city charter, effectively disbanding the Legion as a legal entity. However, a reorganized, unofficial force continued to exist for a short time to protect the Saints during their final preparations to leave Nauvoo in 1846.
Why was the Nauvoo Legion controversial?
The Legion was controversial due to its immense size, the fact that its leader (Joseph Smith) was also a prominent religious figure, and the perception by non-Mormons that it was a private army loyal only to the Church. These factors sparked fears of Mormon political and military dominance, leading to heightened tensions and conflict.

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