Choropleth Map

Choropleth Maps use color, shading, or patterns to define a phenomenon occurring within defined areas. The types of areas vary from county lines to country lines.
The map shown is a Choropleth Map of the Height in inches of men enlisted in World War II by county. This map uses colors and shading to define the average height of the enlistees. The lighter the color the shorter the men; the darker the color the taller the men.


http://www.econ.ucdavis.edu/faculty/jparman/