The American Civil War took place in the United States from 1861 to 1865; between northern states that remained loyal to the Union and southern states that had seceded to establish the Confederate States of America. The long-running debate about the enslavement of African American people was the main cause of the start of the American Civil War. Just over a month after Abraham Lincoln took office as President of the United States, Confederate forces assaulted Fort Sumter in South Carolina in April 1861, sparking the start of the American Civil War. The Union loyalists in the North, which included some geographically western and southern states, declared their support for the Constitution. They were opposed by Confederate States of America secessionists in the South, who campaigned for states' rights to keep slavery.
Two of the first industrial conflicts were also fought during the American Civil War. There was significant technological advancement, particularly in the use of steamships, railroads, the telegraph, and manufactured weapons. Civilian factories, mines, shipyards, banking, transportation, and food supplies were all mobilized, which hinted to the effects of industrialization in World Wars I and II as well as later wars. The conflict continues to be the deadliest in American history. Historically, it has been estimated that 620,000 people died between 1861 and 1865, however a new study contends that 750,000 troops as well as an unknown number of civilians perished.