The American Civil War, widely known in the United States as simply the Civil War as well as other names, was a civil war fought from 1861 to 1865 to determine the survival of the Union or independence for the Confederacy. Among the 34 states in January 1861, seven Southern slave states individually declared their secession from the United States and formed the Confederate States of America. The Confederacy, often simply called the South, grew to include eleven states, and although they claimed thirteen states and additional western territories, the Confederacy was never diplomatically recognized by any foreign country. The states that remained loyal and did not declare secession were known as the Union or the North. The war had its origin in the factious issue of slavery, especially the extension of slavery into the western territories. After four years of combat, which had left around 750,000 Americans, Union and Confederate, dead and had destroyed much of the South's infrastructure, the Confederacy collapsed, and slavery was abolished. Then began the Reconstruction and the processes of restoring national unity and guaranteeing civil rights to the freed slaves.
In the 1860 presidential election, Republicans, led by Abraham Lincoln, supported banning slavery in all the U.S. territories, something the Southern states viewed as a violation of their constitutional rights and as being part of a plan to eventually abolish slavery. The Republican Party, dominant in the North, secured a majority of the electoral votes, and Lincoln was elected the first Republican president, but before his inauguration, seven slave states with cotton-based economies formed the Confederacy. The first six to secede had the highest proportions of slaves in their populations, a total of 48.8 percent. Eight remaining slave states continued to reject calls for secession. Outgoing Democratic President James Buchanan and the incoming Republicans rejected secession as illegal.