Maps To Tell Stories, Maps To Provide Context

There are two major categories of maps. Thematic maps are used to showcase geographic data observations. Thematic maps are almost always associated with storytelling of one kind or another. For example, let’s assume I have a dataset showing the proportion of U.S. citizens who are currently talking about something inane on their cellphones. This hypothetical data might be collected at the county-level, and I’d want to tell a story with my map about which places in the U.S. have the most insipid talkers. The pattern of those observations by county would allow map readers to understand the geographic distribution of those folks, and begin to formulate hypotheses about their causes (places with lots of teenagers, middle-aged men roaming airports, etc…). 

Or you could have a much more serious example, like the one shown below. This map shows the proportion of households in the Lower 48 United States that are headed by women.