Overtime there were many new political disputes causing the tension between the North and South. It started off with the Missouri Compromise. Since the North and South disagreed on the feelings of slavery, they needed a balance of free states and slave states to be fair. Missouri and Maine both wanted to join the union and they could because there were two of them. Missouri was entered as a slave state, and Maine was entered as a free state. Then, the Missouri Compromise line was drawn dividing free states and slave states.
http://teachers.henrico.k12.va.us/tucker/strusky_m/webquests/VUS6_madisonmonroe/MissouriCompromise.html
One of the next disputes was the tariff set on imported goods in 1812. This tariff was set on products from Great Britain such as tea, coffee, sugar, molasses, and other items. Southerners found this tariff to be unfair and believed the government was siding with the North. In response, John Calhoun from South Carolina declared that states should have the right to nullify federal laws. The government disagreed and tensions rose, but eventually, the taxes lowered. Today, states still can not override federal laws under any circumstances. Then, in 1850, California started to become popular because of the gold rush and also wanted to join the Union. The only problem was that if it did join, there would be more free states than slave states. At this time Texas had just won the war against Mexico and also wanted to join, but was in debt. The compromise was that if the USA paid Texas's debt, then Texas could join, but would have to split up into five states which turned into New Mexico, Arizona, Utah, Nevada, and Texas. The South was okay with this compromise because it allowed potential for four new states that could become slave states. Tensions were slowly starting to decrease when the Fugitive Slave Act, and Kansas-Nebraska Act came along. The Fugitive Slave Act meant that Northerners had to help slave catchers that were looking for runaway slaves in the North. The Kansas-Nebraska Act repealed the law about having the line between the slave states and free states, which meant that slavery could be allowed in Nebraska and Kansas if citizens voted for it. These both made Northern abolitionists mad, while pleasing Southerners. Kansas soon became known as "Bleeding Kansas"and became a battleground between Northerners and Southerners.
http://www.pbs.org/wgbh/aia/part4/4p2952.html