- Political Representation: The North had a growing population and increasing political power compared to the South. Northern states generally had more representatives in Congress and the Electoral College, making it easier for them to pass legislation that could potentially affect the institution of slavery.
- Moral Arguments: The abolitionist movement in the North used moral and religious arguments to condemn slavery as inhumane and unjust. This moral pressure fueled Northern support for anti-slavery policies.
- Economic Motives: Some Northerners believed that the expansion of slavery into new territories would give Southern states an unfair economic advantage in agriculture and trade. They feared that this would lead to a decline in Northern industries and a loss of economic opportunities.
- Fugitive Slave Act: In 1850, Congress passed the Fugitive Slave Act as part of the Compromise of 1850. This law required Northern states to return escaped slaves to their masters, even if slavery was illegal in those states. This further strained relations between the North and South and increased concerns about Northern encroachment on Southern rights.
- Compromise of 1850: The Compromise of 1850, while attempting to resolve tensions, also highlighted the growing divide between North and South. The debate over slavery in new territories and the controversy surrounding the Fugitive Slave Act further heightened Southern fears of Northern influence over their institution of slavery.
- Kansas-Nebraska Act: The passage of the Kansas-Nebraska Act in 1854, which allowed the extension of slavery into Kansas and Nebraska despite previously declared free territories, further ignited tensions and intensified the debate over the expansion of slavery. The resulting conflict in Kansas, known as "Bleeding Kansas," heightened the fear of a full-scale conflict between North and South.
These factors combined to create the widespread fear among Southerners that the North would eventually abolish slavery, either gradually or immediately, through political means, moral pressure, or legislation. This fear laid the groundwork for many of the events and conflicts that led to the American Civil War.