From the late 18th to the mid-19th century, various states of the United States allowed the enslavement of human beings, most of whom had been transported from Africa during the Atlantic slave trade or were their descendants. The institution of chattel slavery was established in North America in the 16th century under Spanish colonization, British colonization, French colonization, and Dutch colonization.

After the United States was founded in 1776, the country split into slave states (states permitting slavery) and free states (states prohibiting slavery). Slavery became concentrated in the Southern United States. The Act Prohibiting Importation of Slaves in 1807 banned the Atlantic slave trade, but not the domestic slave trade or slavery itself. Slavery was finally ended throughout the entire country after the American Civil War (1861–1865), in which the U.S. government defeated a confederation of rebelling slave states that attempted to secede from the U.S. in order to preserve the institution of slavery. During the war, U.S. President Abraham Lincoln issued the Emancipation Proclamation, which ordered the liberation of all slaves in rebelling states. In December 1865, the Thirteenth Amendment to the U.S. Constitution was ratified, abolishing chattel slavery nationwide. Native American slave ownership also persisted until 1866, when the federal government negotiated new treaties with the "Five Civilized Tribes" in which they agreed to end slavery.^[1] In June 2021, Juneteenth, a day that commemorates the end of slavery in the U.S., became a federal holiday.

On 22 August 1791, the Haitian Revolution began; it concluded in 1804 with the independence of Haiti. Slavery in Haiti thus came to an end, and Haiti became the second country on the planet that abolished slavery (after the United Kingdom in 1772).^[2][3]

In 1804, Alexander von Humboldt visited the United States and expressed the idea that slavery was not a good way to treat citizens; this was during Thomas Jefferson's presidency. Humboldt's ideas were expanded by the following generation of American politicians, writers, and clergymen, among them Abraham Lincoln and Ralph Waldo Emerson.^[4][5][6]

The growing abolition movement sought to gradually or immediately end slavery in the United States. It was active from the late colonial era until the American Civil War, which culminated in the abolition of American slavery through the Thirteenth Amendment to the United States Constitution.

The Civil War in the United States from 1861 until 1865 was between the United States of America ("the Union" or "the North") and the Confederate States of America (Southern states that voted to secede: "the Confederacy" or "the South").^[a] The central cause of the war was the status of slavery, especially the expansion of slavery into newly acquired land after the Mexican–American War. On the eve of the Civil War in 1860, four million of the 32 million Americans (nearly 13 percent) were black enslaved people, mainly in the southern United States.^[7]

The practice of slavery in the United States was one of the key political issues of the 19th century; decades of political unrest over slavery led up to the war. At the start of the Civil War, there were 34 states in the United States, 15 of which permitted slavery. Before Lincoln took office, seven of these slave states, after conventions devoted to the topic, issued declarations of secession from the United States and created the Confederate States of America. Four more joined them after the war began, and all eleven were represented in the Confederate Congress.^[8][9] The slave states that stayed in the Union — Maryland, Missouri, Delaware, and Kentucky (called border states) — continued to be represented in the U.S. Congress. Because the Emancipation Proclamation, which was issued on January 1, 1863, applied only to states "in rebellion", it did not apply in the border states, nor in Tennessee, because Tennessee was already under Union control.^[10] During the war, the abolition of slavery was required by President Abraham Lincoln for the readmission of Confederate states.^[11]

The U.S. Congress, after the departure of the powerful Southern contingent in 1861, was generally anti-slavery. In a plan endorsed by Abraham Lincoln, slavery in the District of Columbia, which the Southern contingent had protected, was abolished in 1862.^[12] The Union-occupied territories of Louisiana^[13] and eastern Virginia,^[14] which had been exempted from the Emancipation Proclamation, also abolished slavery through state constitutions drafted in 1864. The State of Arkansas, which was not exempt but came partly under Union control by 1864, adopted an anti-slavery constitution in March of that year.^[15] The border states of Maryland (November 1864)^[16] and Missouri (January 1865),^[17] and the Union-occupied Confederate state, Tennessee (January 1865),^[18] all abolished slavery prior to the end of the Civil War, as did the new state of West Virginia (February 1865),^[19] which had separated from Virginia in 1863 over the issue of slavery. However, slavery persisted in Delaware,^[20] Kentucky,^[21] and (to a very limited extent) in New Jersey^[22][23] — and on the books in 7 of 11 of the former Confederate states.

The Emancipation Proclamation was a presidential proclamation and executive order issued by United States President Abraham Lincoln on January 1, 1863, during the Civil War.^[24] Lincoln preceded it with the Preliminary Emancipation Proclamation on September 22, 1862, which read:

That on the first day of January in the year of our Lord, one thousand eight hundred and sixty-three, all persons held as slaves within any State, or designated part of a State, the people whereof shall then be in rebellion against the United States shall be then, thenceforward, and forever free; and the executive government of the United States, including the military and naval authority thereof, will recognize and maintain the freedom of such persons, and will do no act or acts to repress such persons, or any of them, in any efforts they may make for their actual freedom.^[25]

On January 1, 1863, the Proclamation changed the legal status under federal law of more than 3.5 million enslaved African Americans in the secessionist Confederate states from enslaved to free. As soon as an enslaved person escaped the control of his or her master, either by running away across Union lines or through the advance of federal troops, the person was permanently free. Ultimately, the Union victory brought the proclamation into effect in all of the former Confederacy.

On June 19, 1865 — Juneteenth — U.S. Army general Gordon Granger arrived in Galveston, Texas, and announced General Order No. 3, proclaiming freedom for slaves in Texas,^[26] which was the last state of the Confederacy with slavery. Juneteenth has been celebrated annually on June 19 ever since in various parts of the United States. It became a federal holiday in the United States on June 17, 2021, when President Joe Biden signed the Juneteenth National Independence Day Act into law.^[27][28] It is observed not only to commemorate the emancipation of African-American slaves but also to celebrate African-American culture.

During the American Civil War (1861–1865), emancipation came at different times to different places in the Southern United States. Large celebrations of emancipation, often called Jubilees (recalling the biblical Jubilee in which enslaved people were freed) occurred on September 22, January 1, July 4, August 1, April 6, and November 1, among other dates. Although June 19, 1865, was not the actual end of slavery even in Texas (like the Emancipation Proclamation, General Gordon's military order had to be acted upon), and although it has competed with other dates for emancipation's celebration,^[29] ordinary African Americans created, preserved, and spread a shared commemoration of slavery's wartime demise across the United States.^[26]

The Thirteenth Amendment (Amendment XIII) to the United States Constitution abolished slavery and involuntary servitude, except as punishment for a crime. It was passed by the Senate on April 8, 1864, and by the House of Representatives on January 31, 1865.^[30] The Thirteenth Amendment was ratified by the 27th of the then 36 states, fulfilling the constitutional requirement of ratification by 3/4 of states, on December 6, 1865.^[30] Secretary of State William H. Seward announced the passage of the Thirteenth Amendment on December 18, 1865.^[30]

The Thirteenth Amendment was the first of the three Reconstruction Amendments adopted following the American Civil War,^[31] the other two being the Fourteenth and Fifteenth Amendments.

The end of slavery effectively occurred with the federal Padrone Act of 1874 (18 Stat. 251), which was enacted on June 23, 1874, "in response to exploitation of immigrant children in forced begging and street crime by criminalizing the practice of enslaving, buying, selling, or holding any person in involuntary servitude."^[32]

Since the abolition of slavery in the United States in 1865, efforts have been made to eliminate other forms of slavery. In 1890, the Brussels Conference Act adopted a collection of anti-slavery measures to end the slave trade on land and sea. In 1904, the International Agreement for the suppression of the White Slave Traffic was signed. In 1926, the Convention to Suppress the Slave Trade and Slavery was ratified.

Even after slavery became illegal more than a century ago, many criminal organizations continued to engage in human trafficking and slave trading. For this reason, human trafficking was made a federal crime. In 2000, the Victims of Trafficking and Violence Protection Act of 2000 was signed.

In 2014, the Human Trafficking Prevention Act was created. It amended the Trafficking Victims Protection Act of 2000 to require training for federal government personnel related to trafficking in persons.^[33] On 12 Dec 2000 the Protocol to Prevent, Suppress and Punish Trafficking in Persons, Especially Women and Children was adopted by the United Nations General Assembly, and the United Nations Office on Drugs and Crime was put in charge of implementing the protocol. In 2002, the Polaris Project was founded.^[34] Polaris is one of the few organizations working on all forms of trafficking, including both sex trafficking and labor trafficking. It furnishes support for survivors, whether male, female, transgender, or children, and whether U.S. citizens or foreign nationals.^[35]

• The documentary film, 13th, explores the "intersection of race, justice, and mass incarceration in the United States."^[36] Its title alludes to the Thirteenth Amendment to the United States Constitution, adopted in 1865, which abolished slavery and involuntary servitude in the United States, except as a punishment for a crime. The film asserts that slavery has since been silently perpetuated by criminalizing behavior and enabling police to arrest poor black people and forcing them to work for the state. In addition, "carceral states" are managed by for-profit prison corporations.^[37]
• Traces of the Trade: A Story from the Deep North, is a 2008 documentary film that focuses on the descendants of the DeWolf family, a prominent slave-trading family who settled in Bristol, Rhode Island and trafficked Africans from 1769 to 1820, and on the legacy of the slave trade in the North of the United States.^[38][39]

• Slavery in the United States
• Timeline of abolition of slavery and serfdom
• History of civil rights in the United States
• Abolitionism
• Juneteenth
• History of unfree labor in the United States
• Slave Trade Act
• Slavery Abolition Act 1833
• Abolitionism in the United Kingdom
• International Agreement for the suppression of the White Slave Traffic
• Supplementary Convention on the Abolition of Slavery
• Slavery in the 21st century