Final answer:
Manifest Destiny contributed to the expansion of slavery and sectional division between slave states and free states by increasing tensions as new territories were acquired and sought admission to the Union. These tensions, over time, became irreconcilable, leading to the Civil War.
Step-by-step explanation:
The concept of Manifest Destiny significantly furthered the expansion of slavery and fueled sectional division. This ideology, prevalent in the 1840s, advocated that the expansion of the United States across the North American continent was both inevitable and justified, often described as divinely ordained. However, it brought about serious implications for the sectional balance between free and slave states.
The Missouri Compromise initially tried to maintain an equilibrium with the Ohio River serving as a dividing line where states to the south were open to slavery, and those to the north were free.
But as new territories were acquired, such as those from the Mexican-American War, the balance became increasingly difficult to manage, and tensions between free labor North and slave labor South escalated.
Sectional conflicts heightened with each new territory asking to be admitted to the Union and its designated status regarding slavery. The Compromise of 1850, the rising Republican Party, and decisions such as the Dred Scott ruling exacerbated these tensions.
Eventually, the election of Abraham Lincoln, perceived as a threat to the institution of slavery by southern states, led to their secession and the onset of the Civil War.