Answer:
Sectionalism, which is the loyalty or support for a particular region or section of a country over the whole nation, was a major cause of the American Civil War. The conflict was fought from 1861 to 1865 between the United States of America, led by President Abraham Lincoln, and 11 southern states that seceded from the Union and formed the Confederate States of America.
The sectional divide was primarily over the issue of slavery, which was legal in the southern states but had been abolished in the northern states. The southern economy was heavily reliant on agriculture, which was sustained by slave labor, while the northern economy was more industrialized and less dependent on slavery.
The northern states, which were generally opposed to slavery, wanted to abolish it throughout the country, while the southern states felt that their rights to own slaves were being threatened by the federal government. The disagreement over the issue of slavery and state's rights led to the sectional divide, which ultimately led to the Civil War.