The years 1861-1865 mark the period of the American Civil War, a conflict between the Northern states (the Union) and the Southern states (the Confederacy). The war began on April 12, 1861, when Confederate forces attacked Fort Sumter in South Carolina, and it ended on April 9, 1865, with the surrender of Confederate General Robert E. Lee at Appomattox Court House. The Civil War was primarily fought over issues such as slavery, states' rights, and economic differences. It resulted in significant loss of life, with an estimated 620,000 to 750,000 soldiers dying. The war ultimately led to the abolition of slavery in the United States through the 13th Amendment.