There are debated reasons on why the Civil War began. The most common belief is slavery, but many others believe there were other reasons.
Slavery
The North's economy was based on manufacturing, and they got many of their products from the South. One important product from the South was cotton. But many plantation owners hired African slaves to do the work for them. Instead of treating them as workers, they treated them cruelly. Though not all plantation owners did treat them viciously, alot did. There were three blacks for every one white man. People in the North were unaware of the treatment, since they rarely used these black slaves. They only started to realize what was going on when "Uncle Tom's Cabin," by Harriet Beecher Stow, came out. It was a book to tell the country about the cruel treatment going on in the South. Abe Lincoln described her as "the little woman who started a great war."But America was expanding, and slavery began many more problems.
The 3/5 Compromise
The South did not have a very large population. . .or so it seemed, since they didn't count slaves. But once the constitution was written, the realization that a state's amount of representation in the House of Representatives depended on its population became a large issue. The South wanted slaves to count as part of their population, so that they could have more representation. The North disagreed, because the slaves weren't treated as people. So, to settle the conflict, two men, James Wilson and Roger Sherman, proposed the 3/5 compromise. In it, it stated that 3/5 of the slaves would count as the population. The South agreed, but still wanted the slaves to all count.
Nullification Crisis
The 3/5 Compromise, though it worked, increased sectionalism, or, a stronger division between the North and South. The South consisted of plantations and farms with slaves. The North consisted of factories and mills, and they did not use slaves. The problem was, everything was made in the North. Every time Southerners went to buy something, it was made in the North. The South decided they wanted to buy goods from other places, such as Great Britian, France, and Spain. But the North didn't want them to, because then they wouldn't be making a profit. So, they put a tariff, or a tax, on imported goods. This forced the South to buy only from up North. This infuriated the south, and South Carolina nullified the tariff. This began the split between the nation.