The Nauvoo Legion: How the Mormons Built a Private Army

The Latter-day Saints' militia became the largest armed force in Illinois—and a flashpoint for conflict.

By Garret Merkley · Explainer · Jun 4, 2026

Branched from The Founding of Nauvoo: How the Latter-day Saints Built a City of Refuge

Quick take

The Nauvoo Legion was a state-sanctioned militia that grew to 5,000+ members, making it larger than the U.S. Army at the time.
It served as both genuine defense against mob violence and a symbol of Mormon political power that alarmed non-Mormon neighbors.
Internal command structure and Joseph Smith's role as lieutenant general blurred lines between religious authority and military control.
The Legion's existence accelerated tensions that eventually led to Smith's death and the Mormons' expulsion from Illinois.

The Nauvoo Legion was a militia authorized by the Illinois state legislature in 1841 and commanded by Joseph Smith as lieutenant general. At its peak, it enrolled between 2,000 and 5,000 members—making it larger than the standing U.S. Army of that era. Unlike typical state militias, the Legion was almost exclusively composed of Latter-day Saints and functioned as both a defensive force against anti-Mormon mobs and a visible symbol of Mormon military and political power in Illinois.

Why the Mormons Needed an Armed Force

The Latter-day Saints had faced violent persecution in Missouri and Ohio. Mobs destroyed printing presses, burned homes, and drove members from their settlements. When the church relocated to Nauvoo in 1839, Smith and other leaders resolved to build a community that could defend itself. A state-sanctioned militia seemed like the legitimate answer—it would deter attackers and give the Mormons legal standing to bear arms collectively.

The Legion did serve real defensive purposes. It patrolled Nauvoo's borders, responded to threats, and maintained internal order. But it also became something more: a symbol that Mormons were no longer defenseless refugees, but an organized, armed community capable of resisting outside pressure. This shift from victim to power holder alarmed non-Mormon Illinoisans, who began to see the Legion less as a militia and more as a private army.

How the Legion Was Organized and Commanded

The Legion was structured like a conventional military unit, with ranks, companies, and a general staff. Smith held the rank of lieutenant general and served as supreme commander. Other senior church leaders, including Brigham Young and Heber C. Kimball, held officer commissions. The Legion held regular musters—public military drills that were often elaborate ceremonies combining martial display with religious significance.

The critical issue was that command authority flowed through church hierarchy as much as military hierarchy. Smith's role as both prophet and general meant that orders could carry religious weight, blurring the distinction between spiritual obedience and military discipline. Officers were typically church elders, and membership was heavily skewed toward active church members. This made the Legion inseparable from the church itself—a reality that deepened outsiders' suspicion that the Mormons were using military force to enforce religious conformity.

The Flashpoint: Power and Backlash

By the mid-1840s, the Legion's public drills and visible military strength became a lightning rod for anti-Mormon sentiment. Non-Mormon Illinoisans worried that a religiously controlled army could be turned against them. Rumors circulated—some exaggerated, some not—about the Legion's readiness and Smith's intentions. Local newspapers published inflammatory accounts of Legion musters, portraying them as threats to state authority and public safety.

The situation worsened when Smith's political influence grew. He ran for U.S. president in 1844 and made moves to expand Mormon control over local government. Combined with the Legion's visible strength, this convinced many non-Mormons that they faced an organized theocratic state within Illinois. The Legion, once a defensive necessity, became evidence of Mormon ambition—and a justification for violence against them.

Why This Matters and When It Peaked

The Nauvoo Legion represents a crucial moment in American religious history: the collision between a religious community's right to self-defense and the majority's fear of a well-armed religious minority. The Legion was legally authorized, but its existence became politically radioactive. By 1844, anti-Mormon mobs felt justified in taking action, culminating in Smith's arrest and murder in Carthage, Illinois. The Legion's inability or unwillingness to protect Smith signaled that no amount of military organization could overcome the hostility of the surrounding population. Within a few years, the Mormons abandoned Nauvoo and trekked westward, eventually settling in Utah—where they would establish another militia, the Nauvoo Legion's successor.

Key Timeline

1839: Mormons settle Nauvoo, Illinois after expulsion from Missouri
1841: Illinois legislature grants charter authorizing the Nauvoo Legion
1841–1844: Legion grows to 2,000–5,000 members; Smith becomes lieutenant general
1843–1844: Public musters and Smith's political ambitions fuel anti-Mormon backlash
June 1844: Smith arrested in Carthage; Legion fails to prevent his murder
1846: Mormons evacuate Nauvoo; Legion is dissolved

Was the Nauvoo Legion larger than the U.S. Army?

At its peak, yes. The Legion enrolled between 2,000 and 5,000 members, while the U.S. Army in the 1840s had roughly 8,000–10,000 troops spread across the entire country. In terms of concentrated force in a single location, the Legion was unprecedented.

Did the Legion ever actually fight?

The Legion engaged in skirmishes and defensive actions against mobs, particularly in response to raids and threats. However, it never fought a major pitched battle. Its most important role was deterrence—its mere existence was meant to discourage attacks.

Why did the Illinois legislature authorize a militia commanded by a religious leader?

The Nauvoo Charter, granted in 1841, gave the city broad autonomy to organize its own militia. At the time, state militias were common and often commanded by local leaders. The legislature likely did not anticipate how large and religiously cohesive the Legion would become, or how it would be perceived as a threat.

Could the Legion have prevented Joseph Smith's death?

Smith was arrested in Carthage, outside Nauvoo's direct control, and held in a county jail. The Legion mobilized, but by the time they could act, Smith had been killed by a mob. Some historians argue the Legion's strength actually made non-Mormons more determined to eliminate Smith before the Mormons could consolidate power.

What happened to the Nauvoo Legion after the Mormons left Illinois?

The Legion was formally dissolved when Nauvoo was abandoned in 1846. However, the Mormons reorganized militia forces in Utah under a similar name, the Nauvoo Legion, which served the church for decades in the Great Basin.

Sources

Bushman, Richard L. Joseph Smith: Rough Stone Rolling (2005) — comprehensive biography covering the Nauvoo period and the Legion's role.
Flanders, Robert B. Nauvoo: Kingdom on the Mississippi (1965) — detailed history of Nauvoo including militia organization.
Givens, Terryl L. The Viper on the Hearth: Mormons, Myths, and the Construction of Heresy (1997) — analysis of anti-Mormon sentiment and the Legion's symbolic role.