Arlington Gregg circa 1936-40 as part of the WPA Illinois Art Project - Be Kind To Books.
The Works Projects Administration (WPA), previously called the Works Progress Administration were, according to the wisdom that is Wikipedia, "the largest New Deal agency, employing millions to carry out public works projects, including the construction of public buildings and roads, and operated large arts, drama, media, and literacy projects. It fed children and redistributed food, clothing, and housing. Almost every community in the United States had a park, bridge or school constructed by the agency, which especially benefited rural and Western populations."
These posters and many more including one of Milton Glaser's iconic 'Dylan' posters and a 1970's Eric Strenger Porsche poster, are due to be auctioned off at New York's, Swann Galleries Auction, May 3rd 2010 (Sale 2213, Modernist Posters). I could spend a serious amount of money at this auction, so it's probably a good job I'm on the other side of the pond!
All images copyright Swann Galleries.