What are the political and socio economic diffrences between north & south of america in 1850's?alexis de toqueville has written in his book " yet...

The first answer points out some economic differences, so I will talk about political and social differences.

The North was a more egalitarian society.  The South was based on the idea that the big slaveholders were something of an aristocracy.  In the South rich men saw themselves as gentlemen and were concerned about their honor (they fought duels, etc).

Politically, the South believed in confederacy and states' rights.  They worried, more than the North, about having their rights abused by a strong national government.  You can see this in such things as the nullification controversy.