How did the economic and social divide between the north and south need to increase sectionalism and eventually the Civil War

The North was an industrial economy by 1860 and the South continued to be an agricultural economy producing cotton, tobacco, sugar and other things. The southern economy relied heavily on slave labor, which was not the case of the North.

In the decades previous to the Civil War (1861-1865), the different administrations imposed high tariffs to foreign products to protect the American - made northern products. This meant that northern products had usually a high price southerners had to pay for; this originated many claims of a preferential treatment which was damaging for the South and disatisfaction.

And of course, there were the rising tensions over the issue of slavery and whether new states should join the Union as free or slavery states.