In 1861, Union Brigadier General Nathaniel Lyon marched to St. Louis in the divided slave state Missouri to arrest a state militia unit at Camp Jackson that planned to raid a federal arsenal in St. Louis. After capturing the men, the Union 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 explains political divisions still evident in American culture. Included are previously unpublished materials about Governor Claiborne Jackson, the role of Montgomery Blair in the fight for Missouri, and analysis of the number of arms in the St. Louis Arsenal and unknown casualties of the St. Louis massacre.