Sectionalism in 1800s America refers to the different lifestyles, social structures, customs, and political values of the North and the South. It increased steadily in 1800–1850 as the North industrialized, urbanized and built prosperous factories, while the deep South concentrated on plantation agriculture based on slave labor, together with subsistence farming for poor whites who owned no slaves. Southerners defended slavery in part by claiming that Northern factory workers toiled under worse conditions and were not cared for by their employers. Defenders of slavery referred to factory workers as the "white slaves of the North".
Historians do agree that social and cultural institutions were very different in the North and South. In the South, wealthy men owned all of the quality land, leaving poor white farmers with marginal lands of low productivity. Fears of slave revolts and abolitionist activism made the South militantly hostile to suspicious ideas. Southerners argued that the South remained true to the historic republican values of the Founding Fathers (many of whom owned slaves, including Washington, Jefferson and Madison.)
In the North, members and politicians of the newly formed Republican Party were extremely critical of Southern society and argued that the industrial system of wage labor in place in the North resulted in much more prosperity. Republicans criticizing the Southern system of slavery would commonly cite the larger population growth of the Northern states, alongside their rapid growth in factories, farms, and schools as evidence of the superiority of a free labor system. Industrialization meant that seven out of eight European immigrants settled in the North. The movement of twice as many whites leaving the South for the North contributed to the South's defensive-aggressive political behavior.
In the West, the conclusion of manifest destiny and the beginning of the Indian Wars due to mass westward expansion of immigrant and American settlers. The West was settled by poor Americans and immigrants who used the new agricultural technology to make the American West one of the largest agricultural producers in the world. This was the mythology of the Wild West coming to an end, being tamed, and beginning the process of industrialization. In 1867 the transcontinental railroad was completed and the country has since become evermore connected. Today, the "west" - with the exception of large population centers - remain largely rural and based on agriculture.
Sectionalism is used to describe the economic differences of the different regions of the United States in the 19th century, but those economic differences were solely based on the economy of slavery. The Northern factories processed much of the cotton coming from the Southern, slave-holding states and how this economy expanded west would come to define the country. Northern transcendentalists and members of widespread religious revivals viewed slavery as a moral abomination and something incompatible with Christianity. They sought to halt it's spread through the new territories to the West. The South fought to preserve their system of privilege and thus began the Civil War. It was a messy conflict, to be sure, as all wars it was bloody, vengeful, and terrible. But the way it ended defines the parameters of our struggle for equality in America today.