In 1861, Union Brigadier General Nathaniel Lyon marched through the divided slave state Missouri en route to St. Louis. Lyon was to arrest a state militia unit at Camp Jackson that planned to raid a federal arsenal in the city. Upon capturing the men, Lyon's troops encountered crowds of hostile citizens and, after a gun shot, they fired on the mob, killing at least 28 civilians in what is now known as the Camp Jackson affair, or the St. Louis massacre.

In this book, the author describes partisan activities leading to hostilities, promotes awareness about the history of slavery in America, and explores political divisions still evident in American culture. Previously unpublished materials about Governor Claiborne Jackson are included, as well as the role of Montgomery Blair in the fight for Missouri, an analysis of the number of arms in the St. Louis Arsenal and the unknown total number of casualties of the St. Louis massacre.