I’m admittedly not very good with historical precedent, but I think we can all agree it’s important to know about the work those have done before us. It makes your own work better and lets you appreciate what others do more (or less).
To that end, Zach of indiemaps has a fine roundup of the very first thematic maps. The first known choropleth map? That would be Charles Dupinâ€™s from 1826 (above).
How about the first dot density map from FrÃ¨re de Montizon in 1830?