How was the nation divided over the issue of slavery?

It had many causes, but there were two main issues that split the nation: first was the issue of slavery, and second was the balance of power in the federal government. The South was primarily an agrarian society. Throughout the South were large plantations that grew cotton, tobacco and other labor-intensive crops.

The Missouri Compromise—also referred to as the Compromise of 1820—was an agreement between the pro- and anti-slavery factions regulating slavery in the western territories. It prohibited slavery in new states north of the border of the Arkansas territory, excluding Missouri.

Explanation:

basic principles: federalism, separation of powers, checks and balances, judicial review, representative democracy, limited government, rule of law, individual rights and responsibilities, consent of the governed, majority rule, popular sovereignty, equal protection.