The Nauvoo Legion: America's Most Controversial Private Militia

Explore the origins, purpose, and impact of the Nauvoo Legion, a powerful and contentious private militia formed by the Latter-day Saints in 19th-century Illinois.

By Garret Merkley · Explainer · Jun 21, 2026

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

Quick take

The Nauvoo Legion was a large, legally sanctioned Mormon militia in Nauvoo, Illinois, formed under a liberal city charter.
It served as both a defensive force for the Latter-day Saints and a significant source of political and military power for Joseph Smith.
Its size and loyalty to a religious leader fueled intense suspicion and conflict with surrounding communities.
The Legion's existence contributed significantly to the tensions that led to Joseph Smith's death and the eventual exodus of the Mormons from Illinois.

The Nauvoo Legion was a large, privately organized militia established by the Church of Jesus Christ of Latter-day Saints in Nauvoo, Illinois, during the 1840s. Operating under a unique city charter granted by the Illinois state legislature, it functioned as both a local defense force and a significant instrument of political and religious authority for its leader, Joseph Smith.

Origins and Legal Framework

After being driven from Missouri, the Latter-day Saints settled in Nauvoo, Illinois, in 1839. Seeking to protect themselves from further mob violence, they secured an exceptionally broad city charter from the Illinois legislature in 1840. This charter granted Nauvoo extensive autonomy, including the power to raise its own militia, independent of state control. This militia was named the Nauvoo Legion, reviving a name from an earlier Mormon militia in Missouri.

Structure and Purpose

Joseph Smith, the church prophet, was appointed lieutenant general of the Legion, giving him both religious and military command. The Legion was open to all able-bodied men in Nauvoo, and membership was strongly encouraged, if not practically required, for male residents. At its peak, the Legion boasted an estimated 2,000 to 4,000 men, making it one of the largest and best-equipped militias in the United States at the time. Its primary stated purpose was the defense of Nauvoo and its citizens from external threats, but it also served to maintain order within the city and project the political power of the Latter-day Saints.

The Legion held impressive parades and drills, showcasing its strength and discipline. Its uniform varied, but often included military-style attire, and members were expected to provide their own arms. This formidable force allowed Nauvoo to enforce its own laws and protect its unique religious and social practices, often at odds with the surrounding non-Mormon communities.

The Nauvoo Legion's existence is crucial for understanding the escalating tensions between the Latter-day Saints and their neighbors in the 1840s. While intended for protection, its sheer size, loyalty to a single religious leader, and perceived autonomy from state authority deeply alarmed non-Mormons. They viewed it not as a defensive force, but as a private army capable of enforcing Joseph Smith's will and dominating regional politics. This fear was a significant factor contributing to the ongoing conflicts, including the destruction of the Nauvoo Expositor newspaper by city authorities (backed by the Legion) and the eventual assassination of Joseph Smith and his brother Hyrum in June 1844. The Legion's power also played a role in the eventual decision of the Latter-day Saints to abandon Nauvoo and migrate west, as Illinois eventually revoked Nauvoo's charter and disbanded the Legion, leaving the community vulnerable.

Was the Nauvoo Legion legal?

Yes, the Nauvoo Legion was initially formed under a legal city charter granted by the Illinois state legislature. However, its expansive powers and the loyalty it commanded for Joseph Smith led to significant controversy and eventually, the revocation of the charter and disbandment of the Legion by the state.

How large was the Nauvoo Legion?

Estimates vary, but at its peak, the Nauvoo Legion was believed to have between 2,000 and 4,000 armed and trained men. This made it one of the largest and most formidable private militias in the United States at the time.

What happened to the Nauvoo Legion after Joseph Smith's death?

Following Joseph Smith's assassination in 1844, Brigham Young took leadership of the Church. The Legion remained active for a time, but increasing state and federal pressure led to the revocation of Nauvoo's charter in 1845, effectively disbanding the Legion. However, elements of its organizational structure and military experience were carried west and later resurfaced in various forms during the Mormon migration and settlement in Utah.