The Final Toll

 

World War 1 was the bloodiest war in history up to that time. Deaths numbered about 22 million, more than half of them civilians.
The U.S. lost 48,000 men in battle, with another 62,000 dying of disease. More than 200,000 Americans were wounded.

http://www.pbs.org/greatwar/resources/casdeath_pop.html