When the Mormons established their theocratic city of Nauvoo on the banks of the Mississippi in 1839, they made self-defense a priority, having encountered persecution, violence, and forcible expulsion elsewhere. Organized under Illinois law, the Nauvoo Legion was a city militia made up primarily of Latter-day Saints. This comprehensive work on the history, structure, and purpose of the Nauvoo Legion traces its unique story from its founding to the Mormon exodus in 1846. An American construct in design, appearance, and function, the Nauvoo Legion quickly became one of America’s largest―and most feared―militias. The authors describe its origins, daily activities, and general conduct, including parades, sham battles, uniforms, and military operations. And they also present a new interpretation of the Legion’s essential purpose and character.