A Primer on Election Map Cartography

Published on by Jonathan Crowe

With less than two weeks before the 2016 U.S. presidential election, it’s time for a refresher on election map cartography, particularly in the context of U.S. presidential elections.

Cartograms

2012 U.S. presidential results. At right, a cartogram scaled by electoral vote. Maps by Mark Newman.
2012 U.S. presidential results. At right, a cartogram scaled by electoral vote. Maps by Mark Newman.

Let’s start with the basics: at All Over the Map, Greg Miller explains the problem with U.S. presidential election maps—big states with few electoral votes look more important than smaller states with more votes—and introduces the idea of the cartogram: a map distorted to account for some variable other than land area.

Here are some cartograms of the 2012 U.S. presidential results (see above). Previously: Cartograms for the 2008 U.S. Presidential Election Results.

The Map That Started It All

Scribner's statistical atlas of the United States,
Plate 11: Popular Vote: 1880. From Fletcher W. Hewes and Henry Gannett, Scribner’s Statistical Atlas of the United States, 1883. Library of Congress.

Back in 2014, Susan Schulten looked at the map that may have started it all: an 1883 choropleth map of the 1880 U.S. presidential results (see above) that shows results not only on a county-by-county basis, but also the amount the winning candidate won by.

The map may not look advanced today, but in 1883 it broke new ground by enabling Americans to visualize the spatial dynamics of political power. Readers responded enthusiastically. One reviewer pointed to the Republican counties in Arkansas—something left invisible on a map of the Electoral College returns—and wondered what other oddities of geography and history might be uncovered when election returns were more systematically measured. In other words, the map revealed spatial patterns and relationships that might otherwise remain hidden, or only known anecdotally. Perhaps its no coincidence that at the same time the two parties began to launch more coordinated, disciplined, nationwide campaigns, creating a system of two-party rule that we have lived with ever since.

(This map also inverts the modern colours for the two main U.S. political parties: here the Democrats are red and the Republicans are blue. Those colours were standardized only fairly recently.) [Geolounge]

Rethinking Election Map Design

Back to Greg Miller, who has a roundup of different kinds of election maps throughout history, including the maps we’ve seen here so far, Andy Woodruff’s value-by-alpha maps (previously) and others.

For other ways of mapping election results, see this gallery of thematic maps, which includes things like 3D choropleth maps, dot density maps, and all kinds of variations on cartograms and choropleth maps. There’s more than one way to map an election. [Andy Woodruff]