An isoline map is a map with continuous lines joining points of the same value. The map shown above gives the values of the surface dewpoint temperatures across the U.S.
This example of a proportional circle map shows river characteristics derived from hydrologic measurements mad by Lewis & Clark. The area of the circle is proportional to the channel width.
This chloropleth map is from the 2002 Census of Agriculture. A chloropleth map is a map that displays areal data. This map shows the harvested acres of hay in the United States in 2002.