This chapter addresses some of the principles of cartographic design. There are two types of cartographic maps: reference maps and thematic maps. However, matching the type of visual variables with the nature of the data provides little guidance on choosing among the different quantitative thematic maps—namely, choropleth maps, dot density maps, proportional symbol maps, and isarithmic maps. A choropleth map is also referred to as a graduated color map in GIS software. The population density map uses insets to show Alaska, Hawaii, and Puerto Rico. These three insets have different map projections and map scales as indicated by the different scale bars in each of those insets. A map is similar to language in that both are media through which content is communicated. But like a map, visuals are inherently different from letters in that the look of visuals affects interpretation and leaves a lasting impression.