From Robert Krulwich's NPR blog comes a perfect example of what we might call an extended "map argument." Here, Krulwich starts with a political oddity: there's the band of Democtratic voting blue counties in a sea of Republican red that stretches through the Deep South. The perfect set up for a question: Why?
Krulwich, predictably, doesn't start where I might with the demographics of those counties. He gets there, but he goes back much much further in the history of the region to explain why it has ended up being a politically blue place. The reason: plankton 100 million years ago that left the region, millions of years later, with fertile soil. Slave-owning cotton farmers were most successful with their crops in these regions and so brought more slaves. After the Civil War, many former slaves stayed on this land and their families now make up large African-American populations in counties that voted for Obama (the band of blue).
What's impressive to me about Krulwich's argument is his use of maps, layered thematic maps--historical, geological, political, agricultural--to make this case. It operates similar to the "map performances" I've investigated from John King at CNN and with high school students, but in a different format--the blog.