* Total number of deaths: 620,000
* Percentage of population killed: 2.5%
* Leading causes of death: disease, battle wounds, accidents
World War I (1917-1918)
* Total number of deaths: 116,516
* Percentage of population killed: 0.1%
* Leading causes of death: disease, battle wounds, accidents
World War II (1941-1945)
* Total number of deaths: 405,399
* Percentage of population killed: 0.3%
* Leading causes of death: battle wounds, disease, accidents
Korean War (1950-1953)
* Total number of deaths: 36,574
* Percentage of population killed: 0.03%
* Leading causes of death: battle wounds, disease, accidents
Vietnam War (1955-1975)
* Total number of deaths: 58,220
* Percentage of population killed: 0.05%
* Leading causes of death: battle wounds, disease, accidents
Persian Gulf War (1990-1991)
* Total number of deaths: 148
* Percentage of population killed: 0.0001%
* Leading causes of death: battle wounds, accidents
War in Afghanistan (2001-2021)
* Total number of deaths: 2,430
* Percentage of population killed: 0.0002%
* Leading causes of death: battle wounds, disease, accidents
War in Iraq (2003-2011)
* Total number of deaths: 4,487
* Percentage of population killed: 0.0004%
* Leading causes of death: battle wounds, disease, accidents
As can be seen, the American Civil War was by far the deadliest conflict in American history, with a death toll of over 620,000 people. This was due in large part to the fact that the war was fought on a massive scale, with over 2 million men mobilized on both sides. In addition, the war was marked by a high degree of violence, with both sides using new and deadly technologies such as rifled muskets and artillery.
In contrast, the other conflicts listed above were all relatively small in scale, and resulted in far fewer deaths. The Persian Gulf War, for example, lasted only a few months and resulted in the deaths of only 148 Americans. The War in Afghanistan and the War in Iraq were also relatively short-lived, and resulted in the deaths of 2,430 and 4,487 Americans respectively.
It is important to note that these numbers are only estimates, and the true number of deaths in any war is likely to be higher. Additionally, these numbers do not include the deaths of civilians, which can also be significant in times of war.