Uncle Sam “I Want You For US Army" poster

This poster was created in 1917 by illustrator James Montgomery Flagg, originally meant to boost recruitment in the U.S. army in the first World War.

The poster, which depicts Uncle Sam pointing at the viewer above text that reads “I Want You For U.S. Army”, urging the viewer to join the war effort, has become a symbol for American patriotism and has had a lasting legacy with numerous parodies and tributes following its debut in 1917 and is one of the most prominent images of American propaganda.

Uncle Sam's origins can be traced back to the War of 1812 where he became a personification of the American government. The depiction of Uncle Sam seen here was based on the likeness of Flagg himself in order to save on model costs and helped to personalize the urge to enlist in the military. 

The poster originally appeared in a July 1916 issue of Leslie Weekly magazine and debuted as the iconic recruitment poster the following year. 

https://www.warhistoryonline.com/world-war-i/uncle-sam-i-want-you.html