There were many differences between the North and the South in the years not long before the Civil War. These differences were demographic, economic, and cultural.
The major difference between the two was economic. The South’s economy was based on the production and export of staple crops. These were produced on plantations whose workers were slaves. The North’s economy was much more diverse. It had industry, farming for food, services, and many other economic activities. There was no slavery in the North.
Mostly because of slavery, there were demographic differences between the two regions. The North was much more diverse and had many more immigrants. Immigrants did not want to go to the South because there was less opportunity for them in an economy that was dominated by plantations worked by slaves. This meant that there were, for example, not nearly as many Irish and Germans in the South as in the North.
Finally, the two regions had different cultures. The North had a more modern culture while the South had a more archaic culture. Historians generally say that this is because the South was dominated by aristocratic planters whose culture was more similar to that of European gentry than it was to modern Northerners. Southerners valued personal honor and fought duels. Northerners were more interested in making money than in personal honor. This helped make the two regions very different.
In these ways and more, the antebellum North and South were very different places.