Here's a slice from a chart showing the religious affiliations of Americans in 1870: First, these are great because they look like fabric swatches for woolen socks. Secondly, they look remarkably like treemaps but only operate in the horizontal dimension. In the end, it may not be the most readable format, since we end up with some super-skinny slices of Lutherans here and there, but at least it’s easy to see where the Methodists...
