The Slavery Controversy
Probably the most dividing issue was the controversy of slavery. The Northern sphere of the United States began to lean more towards abolition of slavery (this would ensure a more balanced southern economy) while the south heavily depended on slaves for the mass production of crops like cotton, sugar, and tobacco. Also, as the U.S. territory expanded (LA purchase, Mexican-American War, Annexation of Oregon, California, Texas, Arizona, etc.), the debate of whether to expand slavery with it continuously caused contention between north and south.