As the largest city in the fiercely divided border state of Missouri and the most important economic hub on the upper Mississippi River, St. Louis was a major launching point and supply depot for campaigns in the Western and Trans-Mississippi Theaters.
Located at the junction of the Missouri, Illinois and Mississippi Rivers, St. Louis was a major port and commercial center with a rapidly growing industrial base.
It had long served as the starting point for voyages of exploration and emigration into the unsettled West and as the westernmost terminus of many early efforts to construct transcontinental lines of transportation and communication.
Lyon was concerned that Jackson meant to seize the federal arsenal in St. Louis if the state seceded and that the Union had insufficient defensive forces to prevent its capture.
Lyon himself had been extensively involved in the St. Louis Wide Awakes, a pro-Union paramilitary organization that he intended to arm with the arsenal's supplies and muster into the ranks of the federal army.
The Camp Jackson Affair polarized the population of Missouri, leading many once-neutral citizens to advocate secession and setting the stage for sustained violence between the opposing factions.
[4] Returning black Union soldiers like James Milton Turner and Moses Dickson were instrumental in setting up Lincoln University after the Civil War.