Slavery in the United States was a form of slave labor which existed as a legal institution from the early years of the Colonial period. From the sixteenth to the nineteenth centuries, an estimated 12 million Africans were shipped as slaves to the Americas. Of these, an estimated 645,000 were brought to what is now the United States. By the 1860 United States Census, the slave population in the United States had grown to four million.
Under the system that became chattel slavery (ownership of a human being, and of his/her descendants), a racial element was critical: Slaves were blacks of African descent and owned by whites. Children of slave mothers always became slaves themselves. Freedom was only possible by running away (which was difficult and illegal to do), or by manumission by the owner, which was frequently regulated, and sometimes prohibited, by applicable law.
Slavery was integral to the agricultural economies of the South, and thus to the nation's prosperity, in the eighteenth and nineteenth centuries. By 1804, all states north of the Mason and Dixon Line had either abolished slavery outright or passed laws for the gradual abolition of slavery. However, slavery gained new life in the South with the cotton industry after 1800, and expanded into the Southwest. The invention of the cotton gin revitalized cotton production in the South and Southwest, thus increasing the demand for slaves. The nation was polarized into slave and free states along the Mason-Dixon Line, which separated Pennsylvania and Maryland.
Slave labor was in demand in both northern (before 1800) and southern cities as servants. However, the great majority of slaves worked at agriculture on plantations or large farms, where good-quality soil and climate made for labor-intensive cultivation of lucrative cash crops, such as rice, tobacco, sugar, and cotton. In small operations, slaves worked side by side with their owners; on large plantations, they were directed by white paid overseers.
Slaveholders and the commodities of the South had a strong influence on United States politics, and, indeed, many presidents themselves were slaveholders. Slavery was a contentious issue in the politics of the United States from the 1770s through the 1860s, becoming a topic of debate in the drafting of the Constitution; a subject of Federal legislation (such as the ban on the trans-Atlantic slave trade in 1808 and the passage of the Fugitive Slave Act of 1850); and a subject of landmark U.S. Supreme Court cases, such as the Dred Scott decision of 1857.
The treatment of slaves in the United States varied widely depending on conditions, times, and places. Treatment was generally characterized by brutality, degradation, and inhumanity. Whippings, executions, and rapes were commonplace. The colonies and states generally denied slaves the opportunity to learn to read or write, to prevent their forming aspirations that could lead to escape or rebellion. Some slaves learned from planters' children, or from free laborers, if they were working alongside them. Some states prohibited religious gatherings of slaves, fearing that group meetings would facilitate communication and might lead to rebellion.
Slaves were punished by whipping, shackling, hanging, beating, burning, mutilation, branding, and imprisonment. Punishment was most often meted out in response to disobedience or perceived infractions but, sometimes, abuse was carried out simply to re-assert the dominance of the master or overseer over the slave. Because of the power relationships of the institution, slave women in the United States were at high risk for rape and sexual abuse. Many slaves fought back against sexual attacks, and some died resisting. Sexual abuse of slaves was partially rooted in a patriarchal Southern culture that treated all women, black and white, as property or chattel.
By the 1850s, the South was vigorously defending slavery and its expansion into the territories. In the North, a small number of abolitionists denounced it as sinful, and a large number of anti-slavery forces rejected it as detrimental to the rights of free men. Compromises were attempted and failed and in 1861, 11 slave states broke away to form the Confederate States of America, leading to the American Civil War.
The federal government in 1862 made abolition of slavery a war goal. In 1863, President Abraham Lincoln freed slaves in the rebellious southern states through the Emancipation Proclamation. The Thirteenth Amendment, taking effect in December 1865, permanently abolished slavery throughout the entire United States, including the Border states, such as Kentucky, which still had about 50,000 slaves, and the Indian tribes.