These are post cards, although neither has a stamp so they were never mailed. The first has holes at the top where it was pinned up, presumably by a loved one awaiting the soldier’s return. Based on the uniform, I’m pretty confident it dates to World War I.
The second was pretty degraded when I got it, with significant fading and some stains. It was stamped on the back by the photographer, and was taken at Greenfield’s Art Studio, 531 Central Ave, Cincinnati, Ohio. I’m guessing this one is from the same era, although it lacks the distinctive leggings that made me sure about the first one.