You can think of sectionalism as one big neighborhood dispute, and the neighborhood was the United States in the mid-1800s. The nation was divided by its interests, attitudes, and overall lifestyles. Northerners focused on fast-paced business and industry, spending their days manufacturing, shipping, and trading goods. By contract, the Southern economy relied on slow and steady agricultural growth. Planting and picking crops was the work of slaves who supported plantation owners' with their labor.
What was sectionalism in America before the Civil War?
Slavery was the big issue between the North and the South. Abraham Lincoln summed up the consequences of what he saw coming when he said, "A house divided against itself cannot stand." As the country expanded to the west, the edges defining the North and South sections of the nation became razor sharp. Southern states depended on slavery to continue cheap production of cotton, and they wouldn't give up their "rights" to slaves without a fight.
Sectionalism served Abe Lincoln well in the presidential election of 1860. All of the Northern states opposed slavery, so the popular vote went with like-minded Lincoln. The victory spurred 11 Southern states to secede from the union and form the Confederate States of America.
In April 1861, President Lincoln responded to a Confederate Army attack by declaring war. Four years and 600,000 fatalities later, the Confederates surrendered. During the same year as the halt of the Civil War — 1865 — slavery ended officially with the ratification of the 13th Amendment and an assassin cut short the life of Abraham Lincoln.