At the outset of the Civil War, to the dismay of the more radical abolitionists in the North, President Abraham Lincoln did not make abolition of slavery a goal of the Union war effort. To do so, he feared, would drive the border slave states still loyal to the Union into the Confederacy and anger more conservative northerners. By the summer of 1862, however, enslaved people, themselves had pushed the issue, heading by the thousands to the Union lines as Lincoln’s troops marched through the South.

Their actions debunked one of the strongest myths underlying Southern devotion to the “peculiar institution”—that many enslaved people were truly content in bondage—and convinced Lincoln that emancipation had become a political and military necessity. In response to Lincoln’s Emancipation Proclamation, which freed more than 3 million enslaved people in the Confederate states by January 1, 1863, Black people enlisted in the Union Army in large numbers, reaching some 180,000 by war’s end.

Emancipation changed the stakes of the Civil War, ensuring that a Union victory would mean large-scale social revolution in the South. It was still very unclear, however, what form this revolution would take. Over the next several years, Lincoln considered ideas about how to welcome the devastated South back into the Union, but as the war drew to a close in early 1865, he still had no clear plan.

In a speech delivered on April 11, while referring to plans for Reconstruction in Louisiana, Lincoln proposed that some Black people–including free Black people and those who had enlisted in the military–deserved the right to vote. He was assassinated three days later, however, and it would fall to his successor to put plans for Reconstruction in place.

At the end of May 1865, President Andrew Johnson announced his plans for Reconstruction, which reflected both his staunch Unionism and his firm belief in states’ rights. In Johnson’s view, the southern states had never given up their right to govern themselves, and the federal government had no right to determine voting requirements or other questions at the state level.

Under Johnson’s Presidential Reconstruction, all land that had been confiscated by the Union Army and distributed to the formerly enslaved people by the army or the Freedmen’s Bureau (established by Congress in 1865) reverted to its prewar owners. Apart from being required to uphold the abolition of slavery (in compliance with the 13th Amendment to the Constitution), swear loyalty to the Union and pay off war debt, southern state governments were given free rein to rebuild themselves.

As a result of Johnson’s leniency, many southern states in 1865 and 1866 successfully enacted a series of laws known as the “black codes,” which were designed to restrict freed Black peoples’ activity and ensure their availability as a labor force. These repressive codes enraged many in the North, including numerous members of Congress, which refused to seat congressmen and senators elected from the southern states.

In early 1866, Congress passed the Freedmen’s Bureau and Civil Rights Bills and sent them to Johnson for his signature. The first bill extended the life of the bureau, originally established as a temporary organization charged with assisting refugees and formerly enslaved people, while the second defined all persons born in the United States as national citizens who were to enjoy equality before the law. After Johnson vetoed the bills—causing a permanent rupture in his relationship with Congress that would culminate in his impeachment in 1868—the Civil Rights Act became the first major bill to become law over presidential veto.

After northern voters rejected Johnson’s policies in the congressional elections in late 1866, Radical Republicans in Congress took firm hold of Reconstruction in the South. The following March, again over Johnson’s veto, Congress passed the Reconstruction Act of 1867, which temporarily divided the South into five military districts and outlined how governments based on universal (male) suffrage were to be organized. The law also required southern states to ratify the 14th Amendment, which broadened the definition of citizenship, granting “equal protection” of the Constitution to formerly enslaved people, before they could rejoin the Union. In February 1869, Congress approved the 15th Amendment (adopted in 1870), which guaranteed that a citizen’s right to vote would not be denied “on account of race, color, or previous condition of servitude.”

By 1870, all of the former Confederate states had been admitted to the Union, and the state constitutions during the years of Radical Reconstruction were the most progressive in the region’s history. The participation of African Americans in southern public life after 1867 would be by far the most radical development of Reconstruction, which was essentially a large-scale experiment in interracial democracy unlike that of any other society following the abolition of slavery.

Southern Black people won election to southern state governments and even to the U.S. Congress during this period. Among the other achievements of Reconstruction were the South’s first state-funded public school systems, more equitable taxation legislation, laws against racial discrimination in public transport and accommodations and ambitious economic development programs (including aid to railroads and other enterprises).

After 1867, an increasing number of southern whites turned to violence in response to the revolutionary changes of Radical Reconstruction. The Ku Klux Klan and other white supremacist organizations targeted local Republican leaders, white and Black, and other African Americans who challenged white authority. Though federal legislation passed during the administration of President Ulysses S. Grant in 1871 took aim at the Klan and others who attempted to interfere with Black suffrage and other political rights, white supremacy gradually reasserted its hold on the South after the early 1870s as support for Reconstruction waned.

Racism was still a potent force in both South and North, and Republicans became more conservative and less egalitarian as the decade continued. In 1874—after an economic depression plunged much of the South into poverty—the Democratic Party won control of the House of Representatives for the first time since the Civil War.

When Democrats waged a campaign of violence to take control of Mississippi in 1875, Grant refused to send federal troops, marking the end of federal support for Reconstruction-era state governments in the South. By 1876, only Florida, Louisiana and South Carolina were still in Republican hands. In the contested presidential election that year, Republican candidate Rutherford B. Hayes reached a compromise with Democrats in Congress: In exchange for certification of his election, he acknowledged Democratic control of the entire South.

The Compromise of 1876 marked the end of Reconstruction as a distinct period, but the struggle to deal with the revolution ushered in by slavery’s eradication would continue in the South and elsewhere long after that date.

A century later, the legacy of Reconstruction would be revived during the civil rights movement of the 1960s, as African Americans fought for the political, economic and social equality that had long been denied them.