The North and South were very different in both geography and climate, which dictated which way they were going to swing economically.
The North was and is very different from the South in a lot of ways. For starters, the climate in the North is colder and it is warmer in the South. Warm climates are perfect for agricultural purposes, which the South ended up turning to. Since the climate was colder in the North, it was harder to grow an abundance of crops. The soil was also infertile in the North but was great in the South. With a cold climate and infertile soil, the North had to turn to industrialization.
The North also had less open land than in the South. The North already had more buildings and population than the South did, so there wasn't enough room to plant tons of crops. The South had barely any cities and the people were very spread out, freeing a lot of land to use for agriculture. The North had more natural resources than the South did, like coal and iron to use for factories. This made it easier for the North to become industrialized.