Known by several names, the American Civil War (April 12, 1861 – May 9, 1865) was a civil war in the United States fought between the Union (states that stayed faithful to the federal union, or "the North") and the Confederacy (states that remained loyal to the southern states, or "the South") (states that voted to secede, or "the South"). The situation of slavery, and specifically the spread of slavery into territories obtained as a consequence of the Louisiana Purchase and the Mexican–American Conflict, was the primary cause of the war in the United States. Enslaved black people made up approximately 13 % of America's population in 1860, with nearly all of them living in the states in the south before the Civil War broke out.
During the nineteenth century, one of the most contentious political problems in the United States was the system of slavery. The Civil War was the culmination of decades of political upheaval over slavery. Following Abraham Lincoln's election as president of the United States in 1860 on an anti-slavery expansion platform, the country fell into disarray. The Confederacy was formed when an original group of seven southern slave states proclaimed their independence from the United States, becoming the Confederacy. Confederate armies captured federal forts located within the territory they have claimed for themselves. Even though the last-minute Crittenden Compromise attempted to prevent a war, it failed, and both sides prepared for battle. Violence began in April 1861 when the Confederate forces launched the Battle of Sumter in South Carolina, less than a month after Abraham Lincoln was inaugurated as President of the United States. In February 1861, the Confederate had expanded to control at least the majority of land in eleven states (out of the 34 states that made up the United States at the moment). It also claimed claims to two further states. Both sides organised enormous volunteer and conscription armies to fight against each other. Following it, there were four years of severe fighting, especially in the South.