The Emancipation Circuit

The self-liberation or emancipation by flight of at least 400,000 enslaved people followed by the emancipation of the rest of the 4 million blacks in the south produced new social formations within a region already marked by uneven development. Let's define the emancipation circuit, starting with its origins. How did that movement of people create the emancipation circuits nodes? And then what connected those nodes so that they formed this circuit and that endured over time?