This 1921 poster from the ALA is very nice.
On one hand it very much fits into the US self improvement through independent study ethos, as popularised by Andrew Carnegie and to some extent by Ayn Rand – though of course Randians these days don’t like any public services. The worker here is supposedly improving his chances at getting better employment by reading.
It could of course also be seen as an example of Communist/Anarchist art within the noble worker paradigm. The worker studying revolutionary literature to improve everybody’s chances at getting better employment.
Either way, I like the use of the term power within the poster. Whether it is a person’s individual potential or the power of the working class as a whole, it works.
This was brought to my attention by this article http://gizmodo.com/read-to-win-the-war-13-vintage-posters-promoting-ameri-1481958684 which also links to the originals.
For an interesting comparison here is a soviet poster from 1920, which says ‘Knowledge breaks the chains of slavery’