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"). The central
cause of the war was the status of
slavery, especially whether to allow it to expand into territories acquired 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. 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. After Lincoln's election but before he 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. 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 had come under Union control. During the war, the abolition of slavery was required by President
Abraham Lincoln for the readmission of Confederate states. 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. The Union-occupied territories of Louisiana and eastern Virginia, 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. The border states of Maryland (November 1864) and Missouri (January 1865), and the Union-occupied Confederate state, Tennessee (January 1865), all abolished slavery prior to the end of the Civil War, as did the new state of West Virginia (February 1865), which had separated from Virginia in 1863 over the issue of slavery. However, slavery persisted in Delaware, Kentucky, and (to a very limited extent) in New Jersey – and on the books in 7 of 11 of the former Confederate states. == Emancipation Proclamation ==