Which war resulted in the greatest loss of American lives?

The American Civil War resulted in the greatest loss of American lives, with estimates of around 620,000 to 750,000 soldiers dying from combat, disease, and other causes. This conflict, fought between 1861 and 1865, was primarily over issues of slavery and states' rights. The high casualty rate was due to various factors, including the intensity of the fighting and the medical practices of the time. The Civil War's impact on the nation was profound, shaping its future social and political landscape.