Slavery in the United States was the legal institution of chattel slavery that existed in the United States of America in the 18th and 19th centuries after it gained independence and before the end of the American Civil War. Slavery had been practiced in British North America from early colonial days, and was recognized in the Thirteen Colonies at the time of the Declaration of Independence in 1776.
Historically, the status of slave had become a caste associated with African descent, contributing to a system and legacy in which race played an influential role. At the time the United States Constitution was ratified, a relatively small number of free persons of color were among its voting citizens. After the Revolutionary War, abolitionist laws and sentiment gradually spread in the Northern states; in addition, as most of these states had a higher proportion of free labor, they abolished slavery by the end of the 18th century, some with gradual systems that did not free the last slave until the late 1820s. But the rapid expansion of the cotton industry from 1800 in the Deep South after invention of the cotton gin led to the Southern states to depend on slavery as integral to their economy. They attempted to extend it as an institution into the new Western territories. The United States was polarized over the issue of slavery, represented by the slave and free states divided by the Mason-Dixon Line, which separated free Pennsylvania from slave Maryland.
Although the international slave trade was prohibited from 1808, domestic slave trading continued at a rapid pace, driven by demand from the development of cotton cultivation in the Deep South. More than one million slaves were sold from the Upper South, which had a surplus of labor, and taken to the Deep South in a forced migration during the antebellum years, splitting up many families. New communities of African-American culture were developed in the Deep South; the total slave population in the South eventually reached 4 million before abolition.[1][2]
As the West was developed for settlement, the Southern states believed they needed to keep a balance between the number of slave and free states, in order to maintain a political balance of power in Congress. The new territories acquired from Britain, France, and Mexico were the subject of major political compromises. By 1850, the newly rich cotton-growing South was threatening to secede from the Union, and tensions continued to rise. With Southern church ministers having adapted to support of slavery, modified by Christian paternalism, the Baptist and Methodist churches split into regional organizations of the North and South. When Abraham Lincoln won the 1860 election on a platform of no new slave states, the South finally broke away to form the Confederacy; the first six states to secede held the most number of slaves. This marked the start of the Civil War, which caused a huge disruption of the slave economy, with many slaves either escaping or being liberated by the Union armies. The war effectively ended slavery, even before the Thirteenth Amendment (December 1865) formally outlawed the institution throughout the United States.
