If you'd rather get your history in visual than written form, The Graphic Imperative: International Posters for Peace, Social Justice and the Environment 1965-2005 (a mouthful) offers 40 Years of Activist Posters at the Crown Center Gallery (Loyola University) in Chicago.
The event notes quote Pierre Bernard, a French graphic designer as stating that “The poster is the prime field for experimenting with visual
language. It is the scene of changing ideas and aesthetics, of
cultural, social, and political events.”
The exhibit was created by a team from the Massachusetts College of Art and Philadelphia University and first shown at the Massachusetts College of Art in the Fall of 2005.
You can see some of the 121 posters as well as facts and background information on The Graphic Imperative site.
It runs in Chicago until December 19, 2008.
As for practical info on the Crown Center Gallery:
It is located in Rogers Park, steps away from
the Loyola CTA Red Line stop.
Gallery Hours: 10AM-7PM M-F and 12-4pm Sat & Sun and by appointment 773-508-7510
Best of all gallery exhibitions are free, perfect for the Consumed to Thrifty.
Somehow related: Timely Art Exhibit in Madrid: 1914! The Avant-Garde and The Great War