To what extent did teretorial expansion have a negative effect on national unity between 1844 and 1860?

Territorial expansion created new challenges and problems for the federal government. Though new lands provided many economic opportunities, there was a fundamental political issue: as new states are created and incorporated into the Union, should they be slavery states or free states? Before the election of Abraham Lincoln in 1860, some presidents tried hard to strike a balance and preserve the nation's unity. So, territorial expansion fueled tensions and contradictions between abolitionists and slavery supporters.