Wednesday, May 18, 2011

Plato at the Center

Many thanks to my geography student Amy for letting me know about the recent placement of a marker for the U.S. population centroid in Plato, Missouri. Plato is in Texas County, which I have just missed in previous travels in Missouri (my home state from 1977 to 1980).

Amy found the story on the educational web site of the National Ocean Service, part of the National Oceanographic and Atmospheric Administration (NOAA), which also includes such institutions as the National Weather Service. I highly recommend spending some time exploring the NOS pages, which I recently found when looking for educational materials for an article about tides.

The NOS article Do You Know Where Your Centroid Is? describes NOAA's recent involvement in calculating the new population centroid (based on the 2010 census) in the small town of Plato, and the placement of a marker there on May 9 of this year. As explained in the article (and its accompanying audio clip), NOAA's National Geodetic Survey has been responsible for placing such markers since 1960, though the population centroid has been calculated for every census since 1790!

As the map above suggests, western expansion has been a consistent part of the population geography throughout the entire history of the United States. Starting around 1930, however, that westward movement has been combined with a movement toward the south. The NOAA news service provides more details about the celebration in Plato and the demographic history.

The calculation of population centroids requires access to detailed information from the census, but in principle the process is relatively simple. In fact, a county planner and GIS coordinator from New Jersey was able to place the centroid in the right town based on publicly available information released by the census last December. According to a report in the St. Louis Post-Dispatch, Alex Zakrewsky was able to estimate the centroid's location in about 10 minutes. After months of  crunching more detailed data, the Census Bureau and the NGS found that the center was just on the other side of the small town, 3.8 miles from the location Mr. Zakrewsky had identified.
Plato, Missouri basks in its 15 minutes of geographic fame!

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