Map Monday: Peak Population Percentage of US States

Here’s a fun map, made by New York-based information visualization expert (and cartoonist) Dorothy Gambrell, showing “peak state.” In other words, according to the US census, it shows the decade at which each state contained the peak percentage of the US population.

gambrell peak state map

It’s a fun map. Some of the things that catch my eye are the general Westward expansion and the recent dominance of the western states.  (Note that the “peak state” years of the old South remain firmly in the 19th century.)

Also very strange? Michigan. Detroit had a very late population growth spike, in the 1920s to the 1950s, and then cratered in a typical “boomtown” fashion.  Also the line between Montana (1920) and Idaho (2010) is sort of interesting.

Meanwhile, Minnesota peaked as a percentage of the US in 1900, alongside neighboring Wisconsin. This might be one reason why Minnesota is likely to lose a congressional district in the next census reallocation. is a non-profit and is volunteer run. We rely on your support to keep the servers running. If you value what you read, please consider becoming a member.

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4 Responses to Map Monday: Peak Population Percentage of US States

  1. Eric W. May 31, 2016 at 11:25 am #

    I don’t see anything particularly telling about the “old South.” Those states appear to follow the general east-west progression of the rest of the states. In fact, there is a strong correlation between this map and the wikimedia map of U.S. states by date of statehood:

  2. Matty Lang
    Matty Lang May 31, 2016 at 12:06 pm #

    When MN loses a congressional district can we just give up the sixth district and keep everything else the same?

    • robsk May 31, 2016 at 2:26 pm #

      Nice and fun map. My favorite: West Virginia peaked before it was a state.

      My dismal statistics education tells me that there isn’t a strong correlation between this and the wikimedia map. Too many outliers.

      As for the gerrymandered 6th district metro moustache … that’s a-hole ‘nuther can-o-worms.

      • Eric W. May 31, 2016 at 3:31 pm #

        Yeah, I probably overstated it when I said “strong” correlation.

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