It was mainly because of how the North and the South of America had different lifestyles and economy's. You would be surprised to know that the Democratic party back then supported Slavery and the republicans dint support Slavery.
Plain Answer: Because of Slavery, Way of Life and Different Economy. The Democratic Party would do anything to keep themselves supported.
Flat Characters are, well, flat. They don't change much if at all. Round characters are complex as crud and go through lots of change, usually to surprise the reader.
