One of my assignments for LIS 407 (Reference), is to find posters from the 1930s or 1940s that promote libraries.
The LOC site has a ton!
2) from 1940: http://www.loc.gov/pictures/item/98509756/
3) from 1936-1940: http://www.loc.gov/pictures/item/98517823/
4) from 1940: http://www.loc.gov/pictures/item/98509697/
It’s based on “The Thinker.”