Univariate Choropleth Map

Univariate Choropleth maps are the standard choropleth map that displays only one variable with shading or different colors. This is a map of where the most hay is in the United States, with the darker green representing more.

http://www.nass.usda.gov/research/atlas02/Crops/Hay%20and%20Forage%20Crops%20Harvested/Hay%20-%20All%20Hay%20Including%20Alfalfa,%20Other%20Tame,%20Small%20Grain,%20and%20Wild,%20Harvested%20Acres-choropleth%20map.gif