The south was very underdeveloped. They were simply a bunch of plantations in an agrarian society. The south lived off of slaves to do work for their slave owners. This was a major push factor for the south, as the slaves (blacks) would escape to the north to live as free people. One thing that kept the south surviving was the cotton gin, which made cotton very profitable. The north was going through the industrial revolution, with lots of jobs and a growing economy. This was a major pull factor for not just the south, but to the world in general. This was an example of economic opportunity. Another thing the north had was deforestation to make way for new cities and urbanization. The north was industrialist, while the south was agrarian.
