A thematic map displays information regarding a specific data set, such as the average population density in a certain area. A thematic map does not show general geographic features, such as city locations, unless used as a reference point.
Thematic maps were first developed during the 17th century. Development began once general maps showed enough clear details that reference points could be made. One of the first thematic maps was a star chart by Edmond Halley in 1686. A London doctor, John Snow, created a thematic map in 1854 which was used to track the speed of the spread of cholera through the city.