June 27, 2014

Chart of the Week: A century of U.S. political history


Anyone (well, almost anyone) could make a map, or even a series of maps, about party control of Congress over time. But turning that data into an interactive that’s in its own way as addictive as Minecraft or Fruit Ninja is something else again, which is where MapStory comes in.

MapStory is a nonprofit that’s created a online, open-source mapping platform to enable people to create and share data visualizations. Mapmakers have created timeline maps to illustrate everything from charter-school expansion in Minnesota to the proliferation of wind farms across the United States. But this interactive, uploaded to MapStory earlier this month by Jonathan Davis of Arizona State University, stands out both for the sheer amount of information it conveys and how darned fun it is to play with.

Starting in 1918, you can simply play the animation forward to 2012 and watch the shifting patterns of party control of the House of Representatives. Davis’ map also lets you freeze on specific years and zoom in to see individual districts; it also shows the handful of minor-party representatives who’ve gotten themselves elected to Congress over the decades. (That’s catnip for political-trivia buffs: Who knew that the Prohibition Party held a congressional seat in California in the years leading up to the 18th Amendment?)

Comparing past and present, a couple of related points become clear. First, districts have become more and more jigsaw-puzzle-like, as sophisticated mapping software and detailed demographic data have combined to make gerrymandering a fine art. And partly as a consequence, Democratic and Republican seats were more geographically intermixed in 2012 than in 1918, when virtually all seats in the South and Southwest states were held by Democrats and most Northern states were dominated by the GOP.

Category: Chart of the Week

Topics: Congress, U.S. Political Parties

  1. Photo of Drew DeSilver

    is a senior writer at Pew Research Center.


  1. Eli Jackson3 years ago

    Seems to me we moved westward and westward our whole history, spreading out and settling in all the while up til’ maybe the 20s, remaining a rural, God-fearing nation all the while and with the hand of God spurring us on.

    And just in the same way that we all moved off the farm, and out of the country we’ve moved out of the churchhouse and into the den of iniquity.
    We let go of everything good and right, didn’t like the old-time way no-more, now we’re big-city smart-alecs, we know we’re right, we told ourselves so, and therefore god told us so.
    That’s the thinking, and that’s the thinking that’s dooming us, no bible, no hope.

    So what’s the fix?
    Who will make it real?
    Holy Spirit!
    Put down your drug pill and pick up the Gos-pel.

  2. Prentiss Riddle3 years ago

    Interesting, but since dense urban districts are too small to see and sparsely populated rural districts are huge, it effectively omits a lot of information and gives a distorted impression. A representation where each district was represented by a dot or symbol of the same size would be more useful.