Classed Choropleth map

The map above is an example of a classed choropleth map.  Maps of this type display data through a color visualization method.  Each color correlates to a certain range of data output for a certain county.  This classed choropleth map portrays beef cattle emissions in 18992 in all the counties in North Carolina.  The deeper in the red the county gets, the higher they're emissions are.
http://personal.uncc.edu/lagaro/2101/2101_ProjectsS2001/beefmethaneJMK.gif