The American Civil War 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 from the Union to form the Confederate States of America. The civil war began primarily as a result of the long-standing controversy over the enslavement of black people. War broke out in April 1861 when secessionist forces attacked Fort Sumter in South Carolina just over a month after Abraham Lincoln had been inaugurated as the President of the United States. The loyalists of the Union in the North, which also included some geographically western and southern states, proclaimed support for the Constitution. They faced secessionists of the Confederate States in the South, who advocated for states' rights to uphold slavery.
Of the 34 U.S. states in February 1861, seven Southern slave-holding states were declared by their state governments to have seceded from the country, and the Confederate States of America was organized in rebellion against the U.S. constitutional government. The Confederacy grew to control at least a majority of territory in eleven states, 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-holding states, Delaware and Maryland, were invited to join the Confederacy, but nothing substantial developed 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 people dead. 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 black slaves were freed.
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