Choropleth maps

Choropleth maps are a type of Thematic map that is used to show information related to area, typically in the square mile or predetermined political borders. This map shows the production of Hay in the different counties in the US. It was from the USDA website.

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