The Northern and Southern sections of the United States developed along different lines. The South remained a predominantly agrarian economy while the North became more and more industrialized. Different social cultures and political beliefs developed. All of this led to disagreements on issues such as taxes, tariffs and internal improvements as well as states rights versus federal rights.
“The South remained a predominantly agrarian economy while the North became more and more industrialized.”
To be a bit more accurate, the South failed to adapt to changing technology.