Answer:
By sectionalism is meant the period of American history from the War of 1812 to the end of the Civil War, when the United States was divided ideologically, socially, and politically between North and South.
During the War of 1812, America faced Great Britain, which resulted in the closure of European markets, which until then provided manufactured products, and to which raw materials were sold (which were exported mainly from the south). from the country). For this reason, American politicians began to promote the industrialization of the young nation, which took place in the northern sector of the United States, mainly in New York and the Midwest. Thus, in the south of the nation a large part of the economic income was lost, since the British and their allies did not trade with America and therefore the South could not sell their raw material to these nations, while tariffs were established on the industrial imports to promote local industry.
This situation caused a great resentment to be generated between both regions, which was increased by social factors such as the position against slavery, and ended up unleashing the Civil War in 1861.