Partisan maps

I recently got Maps: Finding our Place in the World as a holiday gift. This is the companion book to an exhibit on maps at Chicago's Field Museum. It's a really wonderful book. I've been reading through the chapter on mapping American history by Susan Schulten, a colleague of mine, and I came across Reynold's Political Map of the United States (click to enlarge):
Somehow, I hadn't seen this one before. It's incredible. It was made in 1856, with the clear intent of raising sectional ire among non-slaveholders. The stats along the bottom make clear that slaveholders had a disproportionate share of power. As Reynolds wrote:

Of the 6,222,418 white inhabitants of the South, only 347,525 are owners of slaves. And yet this faction controls every branch of the Federal Government, and wields its influence for the increase and perpetuation of Slavery.

As the book makes clear, this is far from an isolated example of maps being made to serve a political purpose. But I was surprised by how profoundly political this map was. Note the pictures at the top: John C. Frémont and William L. Dayton, the presidential and vice presidential nominees of the Republican Party in 1856. I wonder if the newly-founded Republican Party actually commissioned this map, or if Reynolds was just an avid supporter.