Prior to Harpers Ferry only a small minority of Southerners took secession seriously. Afterwards people in the South began to consider it as an unfortunate step that might be necessary for self-protection. Before Harper's Ferry volunteer militia companies were limited to a few in larger Southern towns and cities; afterwards volunteer companies began organizing in almost every county. Last April I present a paper on John Brown's raid as the antebellum 9-11. It provided uncontestable evidence that abolitionists were in deadly earnest, that Brown and others like him enjoyed the support of influential men in the North, more attacks were coming, and that the life of every Southern man, woman and child was threatened.
It is difficult to imagine the war which followed without John Brown and Harpers Ferry or some other bloody incident like it.