Answer:
Slavery
Explanation:
During 1850 North and South of the US disagreed on the slavery issue. In the Southern states economy was mostly based on cotton and the majority believed that if slavery was abolished then the economy of those states would be ruined.
The Northern states had long abolished slavery, those states had an industrialized economy and called for the abolition of slavery.
With the expansion to the West, the struggles between North and South became even greater, some wanted to expand slavery to the new territories, the North disagreed.
