How many US veterans were alive after world war 1?

Answer 1

Most of them. Mortality among US service personnel in WWI was only about 2-3%. Over 4 million served, and just over 100,000 died. Most of these men died in the last six months of the war, as US forces beame heavily involved after May, 1918. This figure does not include deaths from the worldwide "Spanish Flu" epidemic, which killed many millions around the world, including young, healty soldiers, who sickened and died within a few days from this scourge.

Most of the US dead were members of the US Army. Some units were in action longer than others, and around nine of the forty-two massive divisions the US sent to France suffered significant casualties. There were about 3,600 dead Marines, of al causes. Marines were one-half of the US 2nd Division, which saw a lot of action in the trenches. Only a few hundred sailors died. The air force was part of the US Army through both world wars. It was not large in WWI, and thus its total casualties were a small percentage of the overall loss.

In addition to these 4 million WWI vets there were many thousands of Spanish-America War vets alive in 1918, and thousands of Civil War veterans, and probably a few creaky, ancient Mexican War vets.