Final answer:
The historical circumstances leading up to the Civil War involved increasing tensions between the proslavery South and the antislavery North, ultimately resulting in the secession of seven Deep South states from the Union.
Step-by-step explanation:
The historical circumstances leading up to the Civil War were characterized by increasing tensions between the proslavery South and the antislavery North. The election of Abraham Lincoln in 1860 was a pivotal event that triggered the secession of seven Deep South states from the Union, forming the Confederate States of America. Efforts to preserve the Union failed, and the Civil War ultimately began with the Confederate attack on Fort Sumter. Factors such as economic differences, religion, culture, and ethnicity also played a role in fueling the conflict.