Answer: Cartograms

A cartogram is a rather interesting and curious form of mapping wherein the regular proportions of a map are distorted so that the components of the map (which may be demarcated by countries, states, or even smaller units like counties or townships) are scaled not to their correct geographic size, but to a scale that represents the data the map ties to them.

For example, in the image seen here, the population of the Unites States, circa 1900, is cartographically represented. The far western states, which were then still sparsely populated, are compressed and tiny compared to the much larger northeastern and mid-western states that already had large populations at the turn of the century. If the same cartographic representation of the United States was created with today’s population data using the same methods, the state of California wouldn’t be a tiny sliver on the edge of the map, but one of the largest features on it.

If today’s trivia piqued your interest in cartograms (and possibly shifting population densities), you can click on the link below to play with an interesting and interactive population visualizer based on 220 years worth of U.S. population trends.

U.S. Population Trends Over the Last 220 Years – Ravi Parikh