The Emancipation Proclamation, officially Proclamation 95, was a presidential proclamation and executive order issued by United States President Abraham Lincoln on January 1, 1863, during the Civil War. The Proclamation changed the legal status of more than 3.5 million enslaved African Americans in the secessionist Confederate states from enslaved to free. As soon as slaves escaped the control of their enslavers, either by fleeing to Union lines or through the advance of federal troops, they were permanently free. In addition, the Proclamation allowed for former slaves to "be received into the armed service of the United States."

On September 22, 1862, Lincoln issued the preliminary Emancipation Proclamation. Its third paragraph reads:

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.

On January 1, 1863, Lincoln issued the final Emancipation Proclamation. After quoting from the preliminary Emancipation Proclamation, it stated:

I, Abraham Lincoln, President of the United States, by virtue of the power in me vested as Commander-in-Chief, of the Army and Navy of the United States in time of actual armed rebellion against authority and government of the United States, and as a fit and necessary war measure for suppressing said rebellion, do ... order and designate as the States and parts of States wherein the people thereof respectively, are this day in rebellion, against the United States, the following, towit:

Lincoln then listed the ten states still in rebellion, excluding parts of states under Union control, and continued:

I do order and declare that all persons held as slaves within said designated States, and parts of States, are, and henceforward shall be free.... [S]uch persons of suitable condition, will be received into the armed service of the United States.... And upon this act, sincerely believed to be an act of justice, warranted by the Constitution, upon military necessity, I invoke the considerate judgment of mankind, and the gracious favor of Almighty God....

The proclamation was directed to all of the areas in rebellion and all segments of the executive branch (including the Army and Navy) of the United States. It proclaimed the freedom of enslaved people in the ten states in rebellion. Even though it excluded areas not in rebellion, it still applied to more than 3.5 million of the 4 million enslaved people in the country. Around 25,000 to 75,000 were immediately emancipated in those regions of the Confederacy where the US Army was already in place. It could not be enforced in the areas still in rebellion, but, as the Union army took control of Confederate regions, the Proclamation provided the legal framework for the liberation of more than three and a half million enslaved people in those regions by the end of the war. The Emancipation Proclamation outraged white Southerners and their sympathizers, who saw it as the beginning of a race war. It energized abolitionists, and undermined those Europeans who wanted to intervene to help the Confederacy. The Proclamation lifted the spirits of African Americans both free and enslaved; it led many to escape from their masters and get to Union lines to obtain their freedom and to join the Union Army. The Emancipation Proclamation became a historic document because it "would redefine the Civil War, turning it from a struggle to preserve the Union to one focused on ending slavery, and set a decisive course for how the nation would be reshaped after that historic conflict."The Emancipation Proclamation was never challenged in court. To ensure the abolition of slavery in all of the U.S., Lincoln also insisted that Reconstruction plans for Southern states require them to enact laws abolishing slavery (which occurred during the war in Tennessee, Arkansas, and Louisiana); Lincoln encouraged border states to adopt abolition (which occurred during the war in Maryland, Missouri, and West Virginia) and pushed for passage of the Thirteenth Amendment. The Senate passed the 13th Amendment by the necessary two-thirds vote on April 8, 1864; the House of Representatives did so on January 31, 1865; and the required three-fourths of the states ratified it on December 6, 1865. The amendment made slavery and involuntary servitude unconstitutional, "except as a punishment for crime."

The legal institution of human chattel slavery, comprising the enslavement primarily of Africans and African Americans, was prevalent in the United States of America from its founding in 1776 until the ratification of the Thirteenth Amendment on December 6, 1865. The Amendment prohibited "slavery [and] involuntary servitude, except as a punishment for crime."Slavery was established throughout European colonization in the Americas. From 1526, during early colonial days, it was practiced in Britain's colonies, including the Thirteen Colonies that formed the United States. Under the law, an enslaved person was treated as property and could be bought, sold, or given away. Slavery lasted in about half of U.S. states until its abolition in 1865. In the decades after the end of Reconstruction, many of slavery's economic and social functions were continued through segregation, sharecropping, and convict leasing.

By the time of the American Revolution (1775–1783), the status of enslaved people had been institutionalized as a racial caste associated with African ancestry. During and immediately following the Revolution, abolitionist laws were passed in most Northern states and a movement developed to abolish slavery. The role of slavery under the United States Constitution (1789) was the most contentious issue during its drafting. Although the creators of the Constitution never used the word "slavery", the final document, through the three-fifths clause, gave slave owners disproportionate political power by augmenting the congressional representation and the Electoral College votes of slaveholding states. All Northern states had abolished slavery in some way by 1805; sometimes, abolition was a gradual process, and hundreds of people were still enslaved in the Northern states as late as the 1840 Census. Some slaveowners, primarily in the Upper South, freed their slaves, and philanthropists and charitable groups bought and freed others. The Atlantic slave trade was outlawed by individual states beginning during the American Revolution. The import trade was banned by Congress in 1808, although smuggling was common thereafter.: 7  It has been estimated that about 30% of congressmen who were born before 1840 were, at some time in their lives, owners of slaves. Some have argued that this affected the progress of legislation against slavery.The rapid expansion of the cotton industry in the Deep South after the invention of the cotton gin greatly increased demand for slave labor, and the Southern states continued as slave societies. The United States became ever more polarized over the issue of slavery, split into slave and free states. Driven by labor demands from new cotton plantations in the Deep South, the Upper South sold more than a million slaves who were taken to the Deep South. The total slave population in the South eventually reached four million. As the United States expanded, the Southern states attempted to extend slavery into the new western territories to allow proslavery forces to maintain their power in the country. The new territories acquired by the Louisiana Purchase and the Mexican Cession were the subject of major political crises and compromises. By 1850, the newly rich, cotton-growing South was threatening to secede from the Union, and tensions continued to rise. Slavery was defended in the South as a "positive good", and the largest religious denominations split over the slavery issue into regional organizations of the North and South.

When Abraham Lincoln won the 1860 election on a platform of halting the expansion of slavery, seven slave states seceded to form the Confederacy. Shortly afterward, the Civil War began on April 12, 1861, when Confederate forces attacked the U.S. Army's Fort Sumter in Charleston, South Carolina. Four additional slave states then joined the confederacy after Lincoln, on April 15, called forth in response "the militia of the several States of the Union, to the aggregate number of seventy-five thousand, in order to suppress [the rebellion]." Due to Union measures such as the Confiscation Acts and the Emancipation Proclamation in 1863, the war effectively ended chattel slavery in most places. Following the Union victory in May 1865, and upon ratification of the Thirteenth Amendment in December 1865, chattel slavery was abolished in any place subject to the jurisdiction of the United States.