univariate choropleth map

http://www.colocarto.com/custom-thematic-maps.html

A univariate choropleth map displays data from a single variable with the use of shades from a single color. The map above has shades of orange-reddish to document the estimated household income of each state in the U.S. This is the only variable being displayed, and it is using shades from a single color to do so.