Final answer:
The main concern for both the Northern and Southern states in the 1850s was the issue of slavery in the territories of the West. Northerners and Southerners had different views on social mobility and defended their positions on slavery, leading to growing tensions and sectional conflict.
Step-by-step explanation:
In the late 1840s and early 1850s, the main concern for both the Northern and Southern states was the issue of slavery with regards to the territories in the West. Northerners saw the extension of slavery as a threat to their way of life based on principles of free labor, while Southerners believed they needed to expand slavery to preserve their way of life built on the institution of slavery. Both sides had different views on social mobility and sought to defend their positions on slavery, which ultimately led to growing tensions and the unraveling of the sectional balance.