The American Civil War (also known by other names) was a civil war in the United States from 1861 to 1865, fought between northern states loyal to the Union and southern states that had seceded to form the Confederate States of America. The principal cause of the war was whether the enslavement of black people in the southern states should continue.
After Abraham Lincoln won the November 1860 presidential election on an anti-slavery platform, an initial seven slave states declared their secession from the country to form the Confederacy. War broke out in April 1861 when secessionist forces attacked Fort Sumter in South Carolina, just over a month after Lincoln's inauguration. An additional four slave states joined the Confederacy in the following two months. The Confederacy grew to control at least a majority of territory in those eleven states (out of the 34 U.S. states in February 1861), and it claimed the additional states of Kentucky and Missouri by assertions from native secessionists fleeing Union authority. These states were given full representation in the Confederate Congress throughout the Civil War. The two remaining slave states, Delaware and Maryland, were invited to join the Confederacy, but Delaware declined and nothing substantial developed in Maryland due to intervention by federal troops.
The Confederate states were never diplomatically recognized as a joint entity by the government of the United States, nor by that of any foreign country. The states that remained loyal to the U.S. were known as the Union. The Union and the Confederacy quickly raised volunteer and conscription armies that fought mostly in the South for four years. Intense combat left between 620,000 and 750,000 soldiers dead, along with an undetermined number of civilians. The Civil War remains the deadliest military conflict in American history, and accounted for more American military deaths than all other wars combined until the Vietnam War.
The war effectively ended on April 9, 1865, when Confederate General Robert E. Lee surrendered to Union General Ulysses S. Grant at the Battle of Appomattox Court House. Confederate generals throughout the Southern states followed suit, the last surrender on land occurring June 23. Much of the South's infrastructure was destroyed, especially its railroads. The Confederacy collapsed, slavery was abolished, and four million enslaved Black people were freed. The war-torn nation then entered the Reconstruction era in a partially successful attempt to rebuild the country and grant civil rights to freed slaves.
The Civil War is one of the most studied and written about episodes in U.S. history, and remains the subject of cultural and historiographical debate. Of particular interest are the causes of the Civil War and the persisting myth of the Lost Cause of the Confederacy. The American Civil War was among the earliest industrial wars. Railroads, the telegraph, steamships and iron-clad ships, and mass-produced weapons were employed extensively. The mobilization of civilian factories, mines, shipyards, banks, transportation, and food supplies all foreshadowed the impact of industrialization in World War I, World War II, and subsequent conflicts.