Sources:  Congressional Research Service:

List Notes: List is military deaths in principal wars in which the United States participated. Deaths include combat and non-combat deaths. Wounded are non-mortal wounds. Please note: Union records of losses were more accurately kept whereas Confederate records were not kept or destroyed during the American Civil War. Losses during the American Civil War are estimated by statisticians to be between 618,000 to 700,000. Also please consider that exact figures are difficult to find with respect to wars and these numbers should be viewed as near estimates because of the different definitions used for each category, the questionable accuracy of the recording systems used and the loss or destruction of a number of official documents.