About 620,000 Americans, or 2% of the population, died in the American Civil War. That's proportionally equivalent to 6 million people today.
The US Civil War took place between the Northern states (Union) and the Southern states (Confederacy) between 1861 and 1865. The victory of the North ended slavery and formed the American states into a unified nation. The price however, was the lives of 620,000 people. This was 2% of the American population. as there were a little over 31 million US residents at the time.
The American Civil War was the conflict with the highest death toll in the world after the 1815 Napoleonic Wars and until World War I in 1914. It is also the American war with the highest number of military deaths, followed by 405,399 deaths in World War II.
More about the US Civil War:
The civil war and all wars were tragic so I would like to bring your attention to another war in the United States in which our military, our citizens and our children are being betrayed. The war is on the American people by the illegal alien invasion sanction by your government and others.
About 116,353 Americans have been killed by illegal aliens since 9/11 according to figures by Rep Steve King of Iowa who says 25 Americans are killed daily by illegal invaders. About 12 Americans a day are killed by drunk illegal alien drivers who think it's "macho" to drive drunk.