The American Civil War was a war fought in the United States from 1861 to 1865. As a result of the long-standing controversy over slavery, war broke out in April 1861, when Confederate forces attacked Fort Sumter in South Carolina, shortly after U.S. President Abraham Lincoln was inaugurated. The nationalists of the Union proclaimed loyalty to the U.S. Constitution. They faced secessionists of the Confederate States, who advocated for states' rights to expand slavery.
Among the 34 U.S. states in February 1861, seven Southern slave states individually declared their secession from the U.S. to form the Confederate States of America, or the South. The Confederacy grew to include eleven slave states. The Confederacy was never diplomatically recognized by the United States government, nor was it recognized by any foreign country. The states that remained loyal to the U.S. were known as the Union or the North.
The Union and Confederacy quickly raised volunteer and conscription armies that fought mostly in the South over four years. The Union finally won the war when General Robert E. Lee surrendered to General Ulysses S.