In the summer and fall of 1838, animosity between Mormons and their neighbors in western Missouri erupted into an armed conflict known as the Mormon War. The conflict continued until early November, when the outnumbered Mormons surrendered and agreed to leave the state.

In this major new interpretation of those events, LeSueur argues that while a number of prejudices and fears stimulated the opposition of Missourians to their Mormon neighbors, Mormon militancy contributed greatly to the animosity between them. Prejudice and poor judgment characterized leaders on both sides of the struggle. In addition, LeSueur views the conflict as an expression of attitudes and beliefs that have fostered a vigilante tradition in the United States. The willingness of both Missourians and Mormons to adopt extralegal measures to protect and enforce community values led to the breakdown of civil control and to open warfare in northwestern Missouri.