Dot Distribution Maps

The map above shows the distribution of public libraries throughout the U.S. Each dot is representative of a single library in that location. As opposed to proportional circles, the dots allow for a visual aid to represent density of the variable. One can easily see where the highest concentration of libraries are right away. These characteristics classify the image above as a dot distribution map.

http://gothos.info/2013/03/the-geography-of-us-public-libraries/