The war before the war

"For decades after its founding, America was really two nations–one slave, one free. There were many reasons why this composite nation ultimately broke apart, but the fact that enslaved black people repeatedly risked their lives to flee their masters in the South in search of freedom in the North proved that the “united” states was actually a lie. Fugitive slaves exposed the contradiction between the myth that slavery was a benign institution and the reality that a nation based on the principle of human equality was in fact a prison-house in which millions of Americans had no rights at all. By awakening northerners to the true nature of slavery, and by enraging southerners who demanded the return of their human “property,” fugitive slaves forced the nation to confront the truth about itself"--