Classification is commonplace in thematic cartography. In choropleth mapping, classification is the norm. This was not always so. The first choropleth map (created by Baron Charles Dupin in 1826) was unclassed.
According to Arthur Robinson, in his Early Thematic Mapping in the History of Cartography:
So far as we now know, the [...]
I’m kind of on a cartogram kick lately. I’m interested in the pioneers of the form, those who first thought to distort borders and explode topologies in order to convey the distribution of some thematic variable. When was the first cartogram produced, where, and by whom? I ran into a lot of [...]
notes on noncontiguous cartograms and ActionScript 3 classes for producing them
Fully contiguous cartograms have stretched and distorted borders but perfectly maintained topologies. Like the Gastner-Newman diffusion-based cartograms we see all over the place. Though all sorts of cartogram designs have been produced, those with perfect topology preservation (fully contiguous cartograms) receive the majority of [...]