Most soldiers in WW1 were young men, with the majority between the ages of 18 and 21. However, soldiers as young as 16 enlisted, and some older men in their late 30s and early 40s also served. The draft, implemented in 1917, required men aged 21 to 30 to register, later expanding to ages 18 to 45.
Ethnicity: The U.S. military was predominantly made up of white soldiers, but it also included African Americans, Native Americans, Mexican Americans, and immigrants from various backgrounds. African American soldiers served in segregated units, with many assigned to labor or support roles, though some fought in combat units like the 369th Infantry Regiment (the "Harlem Hellfighters"). The Choctaw Code Talkers were in the 36th Infantry Division, 146th Infantry Regiment.
The soldier you see here is wearing the Army's winter service uniform, made of olive drab wool in contrast to the olive cotton worn in warm weather. The style marks the first time the service uniforms were solely one color, and did not include a topcoat or trousers. They were the standard field and combat choice for troops in Europe during WWI.
Learn more about the evolution of U.S. military uniforms here.