In the 17th and 18th centuries, enslaved Africans worked mainly on the tobacco, rice and indigo plantations of the southern coast, from the Chesapeake Bay colonies of Maryland and Virginia south to Georgia. Starting 1662, the colony of Virginia and then other English colonies established that the legal status of a slave was inherited through the mother. As a result, the children of enslaved women legally became slaves.

Before the rise of the American Revolution, the first debates to abolish slavery emerged. Black and white abolitionists contributed to the enactment of new legislation gradually abolishing slavery in some northern states such as Vermont and Pennsylvania. However, these laws emancipated only the newly born children of enslaved women.

But after the end of the American Revolutionary War, slavery was maintained in the new states. The new U.S. Constitution tacitly acknowledged the institution of slavery, when it determined that three out of every five enslaved people were counted when determining a state's total population for the purposes of taxation and representation in Congress.

Throughout the 17th and 18th centuries, European and American slave merchants purchased enslaved Africans who were transported to the Americas and forced into slavery in the American colonies and exploited to work in the production of crops such as tobacco, wheat, indigo, rice, sugar, and cotton. Enslaved men and women also performed work in northern cities such as Boston and New York, and in southern cities such as Charleston, Richmond, and Baltimore.

By the mid-19th century, America’s westward expansion and the abolition movement provoked a great debate over slavery that would tear the nation apart in the bloody Civil War. Though the Union victory freed the nation’s four million enslaved people, the legacy of slavery continued to influence American history, from the Reconstruction to the civil rights movement that emerged a century after emancipation and beyond.

In the late 18th century, the mechanization of the textile industry in England led to a huge demand for American cotton, a southern crop planted and harvested by enslaved people, but whose production was limited by the difficulty of removing the seeds from raw cotton fibers by hand.

But in 1793, a U.S.-born  schoolteacher named Eli Whitney invented the cotton gin, a simple mechanized device that efficiently removed the seeds. His device was widely copied, and within a few years, the South transitioned from the large-scale production of tobacco to that of cotton, a switch that reinforced the region’s dependence on enslaved labor.

Slavery was never widespread in the North as it was in the South, but many northern businessmen grew rich on the slave trade and investments in southern plantations. Although gradual abolition emancipated newborns since the late 18th century, slavery was only abolished in New York in 1827, and in Connecticut in 1848.

Though the U.S. Congress outlawed the African slave trade in 1808, the domestic trade flourished, and the enslaved population in the United States nearly tripled over the next 50 years. By 1860 it had reached nearly 4 million, with more than half living in the cotton-producing states of the South.

Enslaved people in the antebellum South constituted about one-third of the southern population. Most lived on large plantations or small farms; many enslavers owned fewer than 50 enslaved people.

Landowners sought to make their enslaved completely dependent on them through a system of restrictive codes. They were usually prohibited from learning to read and write, and their behavior and movement were restricted.

Many enslavers raped women they held in slavery, and rewarded obedient behavior with favors, while rebellious enslaved people were brutally punished. A strict hierarchy among the enslaved (from privileged house workers and skilled artisans down to lowly field hands) helped keep them divided and less likely to organize against their enslavers.

Marriages between enslaved men and women had no legal basis, but many did marry and raise large families. Most owners of enslaved workers encouraged this practice, but nonetheless did not usually hesitate to divide families by sale or removal.

Enslaved people organized rebellions as early as the 18th century. In 1739, enslaved people led the Stono Rebellion in South Carolina, the largest slave rebellion during the colonial era in North America.  Other rebellions followed, including the one led by  Gabriel Prosser in Richmond in 1800 and by Denmark Vesey in Charleston in 1822. These uprisings were brutally repressed.

The revolt that most terrified enslavers was that led by Nat Turner in Southampton County, Virginia, in August 1831. Turner’s group, which eventually numbered as many 50 Black men, murdered some 55 white people in two days before armed resistance from local white people and the arrival of state militia forces overwhelmed them.

Like with previous rebellions, in the aftermath of the Nat Turner’s Rebellion, slave owners feared similar insurrections and southern states further passed legislation prohibiting the movement and assembly of enslaved people.

As slavery expanded during the second half of the 18th century,  a growing abolitionist movement emerged in the North.

From the 1830s to the 1860s, the movement to abolish slavery in America gained strength, led by formerly enslaved people  such as Frederick Douglass and white supporters such as William Lloyd Garrison, founder of the radical newspaper The Liberator.

While many abolitionists based their activism on the belief that slaveholding was a sin, others were more inclined to the non-religious “free-labor” argument, which held that slaveholding was regressive, inefficient and made little economic sense.

Black abolitionists  and antislavery northerners led meetings and created newspapers. They also had begun helping enslaved people escape from southern plantations to the North via a loose network of safe houses as early as the 1780s. This practice, known as the Underground Railroad, gained real momentum in the 1830s.

Conductors like Harriet Tubman guided escapees on their journey North, and “stationmasters” included such prominent figures as Frederick Douglass, Secretary of State William H. Seward and Pennsylvania congressman Thaddeus Stevens. Although no one knows for sure how many men, women, and children escaped slavery through the Underground Railroad, it was in the thousands (estimates range from 25,000 to 100,000).

The success of the Underground Railroad helped spread abolitionist feelings in the North. It also undoubtedly increased sectional tensions, convincing pro-slavery southerners of their northern countrymen’s determination to defeat the institution that sustained them.

America’s explosive growth—and its expansion westward in the first half of the 19th century—would provide a larger stage for the growing conflict over slavery in America and its future limitation or expansion.

In 1820, a bitter debate over the federal government’s right to restrict slavery over Missouri’s application for statehood ended in a compromise: Missouri was admitted to the Union as a slave state, Maine as a free state and all western territories north of Missouri’s southern border were to be free soil.

Although the Missouri Compromise was designed to maintain an even balance between slave and free states, it was only temporarily able to help quell the forces of sectionalism.

In 1850, another tenuous compromise was negotiated to resolve the question of slavery in territories won during the Mexican-American War.

Four years later, however, the Kansas-Nebraska Act opened all new territories to slavery by asserting the rule of popular sovereignty over congressional edict, leading pro- and anti-slavery forces to battle it out—with considerable bloodshed—in the new state of Kansas.

Outrage in the North over the Kansas-Nebraska Act spelled the downfall of the old Whig Party and the birth of a new, all-northern Republican Party. In 1857, the Dred Scott decision by the Supreme Court (involving an enslaved man who sued for his freedom on the grounds that his enslaver had taken him into free territory) effectively repealed the Missouri Compromise by ruling that all territories were open to slavery.

In 1859, two years after the Dred Scott decision, an event occurred that would ignite passions nationwide over the issue of slavery.

John Brown’s raid on Harper’s Ferry, Virginia—in which the abolitionist and 22 men, including five Black men and three of Brown’s sons raided and occupied a federal arsenal—resulted in the deaths of 10 people and Brown’s hanging.

The insurrection exposed the growing national rift over slavery: Brown was hailed as a martyred hero by northern abolitionists but was vilified as a mass murderer in the South.

The South would reach the breaking point the following year, when Republican candidate Abraham Lincoln was elected as president. Within three months, seven southern states had seceded to form the Confederate States of America; four more would follow after the Civil War began.

Though Lincoln’s anti-slavery views were well established, the central Union war aim at first was not to abolish slavery, but to preserve the United States as a nation.

Abolition became a goal only later, due to military necessity, growing anti-slavery sentiment in the North and the self-emancipation of many people who fled enslavement as Union troops swept through the South.

On September 22, 1862, Lincoln issued a preliminary emancipation proclamation, and on January 1, 1863, he made it official that “slaves within any State, or designated part of a State…in rebellion,…shall be then, thenceforward, and forever free.”

By freeing some 3 million enslaved people in the rebel states, the Emancipation Proclamation deprived the Confederacy of the bulk of its labor forces and put international public opinion strongly on the Union side.

Though the Emancipation Proclamation didn’t officially end all slavery in America—that would happen with the passage of the 13th Amendment after the Civil War’s end in 1865—some 186,000 Black soldiers would join the Union Army, and about 38,000 lost their lives.

The 13th Amendment, adopted on December 18, 1865, officially abolished slavery, but freed Black peoples’ status in the post-war South remained precarious, and significant challenges awaited during the Reconstruction period.

Previously enslaved men and women received the rights of citizenship and the “equal protection” of the Constitution in the 14th Amendment and the right to vote in the 15th Amendment, but these provisions of the Constitution were often ignored or violated, and it was difficult for Black citizens to gain a foothold in the post-war economy thanks to restrictive Black codes and regressive contractual arrangements such as sharecropping.

Despite seeing an unprecedented degree of Black participation in American political life, Reconstruction was ultimately frustrating for African Americans, and the rebirth of white supremacy—including the rise of racist organizations such as the Ku Klux Klan (KKK)—had triumphed in the South by 1877.

Almost a century later, resistance to the lingering racism and discrimination in America that began during the slavery era led to the civil rights movement of the 1960s, which achieved the greatest political and social gains for Black Americans since Reconstruction.

Ana Lucia Araujo, a historian of slavery and the Atlantic slave trade, edited and contributed to this article. Dr. Araujo is currently Professor of History at Howard University in Washington, D.C., and member of the International Scientific Committee of the UNESCO Routes of Enslaved Peoples Projects. Her three more recent books are Reparations for Slavery and the Slave Trade: A Transnational and Comparative History, The Gift: How Objects of Prestige Shaped the Atlantic Slave Trade and Colonialism, and Humans in Shackles: An Atlantic History of Slavery.