Well the labor market was certainly less free, for one :) It's worth knowing that the south was once considerably richer than the north, but industrialisation

Well the labor market was certainly less free, for one :) It's worth knowing that the south was once considerably richer than the north, but industrialisation changed things in the 19th C, by the end of which the north was vastly richer (per capita), richer than anywhere had ever been before. In this sense free capitalism did vastly outcompete an unfree economy.