In the mid 1800's the United States was divided by sectionalism. All the areas of the country were arguing over whether the states had the right and the power to overturn federal law, and whether or not slavery was constitutional. These big disputes were generally between the North and the South, because each region had a different economy. The North was industrial while the South was agriculturally. These issues led to mistrust between the regions and eventually to the civil war.
One of the two main issues that created sectionalism is nullification. Nullification is defined as the act of a state refusing to uphold and enforce federal law. In the 1930's South Carolina declared that the tariff acts of 1828 and 1832 are unauthorized by the constitution of the United States and there for violate the peoples rights, and that from that point on the tariff acts were considered null and void.
This statement made the North especially the president furious so he in turn went down to South Carolina with fifty thousand militia and told them that he would use force if necessary to keep one complete union. Both of these actions left tensions high between both the North and the South.
The second main issue that attributed to sectionalism was slavery. Now slavery is the practice of forcing a person (in this case an African American) to work and live on your land. They are considered property of the master and just like property they can be sold when their use has become non-profitable. The south relied on slavery to maintain their way of life. Were as the north was more industrialized and didn't require the use of slave labor.
Not everyone felt the same about these issues, each region had a different opinion about the different issues.