Dot Distribution Map: U.S. Population Density

http://www.census.gov/geo/www/mapGallery/2kpopden.html

This is an example of a dot density map prepared by the U.S. Census Bureau in 2000. These types of maps are used to show the quantity of data or property by placing a dot in a geographic unit for each type of specified data point or property. These are also known as point pattern maps that use nonproportional point symbols. The dots are set to a specific scale or number that does not vary. Here, one dot equals 7,500 people. It shows across the U.S. the areas with greater or lesser population by the concentration of dots within an area.