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American Centroid Helps To Trace Path Of U.S. Migration


Imagine if you will, a perfectly flat map of America. All 308 million Americans are standing where they live. Each person weighs the same. One precise location is the balancing point with equal weight in all directions. And this point has a name. It's called the American Centroid.

And it's calculated every 10 years by the National Oceanic and Atmospheric Administrations, using the latest U.S. census data. Jeremy Miller wrote about the significance of the American Centroid for the latest edition of Orion Magazine and he joins us on the line to talk about it. Jeremy, welcome.

JEREMY MILLER: Thank you for having me.

GREENE: So, I guess the burning question I have, is where is the American Centroid now?

MILLER: Well, right now the marker designating the centroid is in a little town called Plato, Missouri, roughly 100 miles southwest of St. Louis. The actual centroid, however, falls out in the middle of Mark Twain Forest.

GREENE: So you don't always put the marker in the precise location where the centroid is. You have to find somewhere that you're able to get to it easily.

MILLER: Exactly.

GREENE: Well, what's the appeal? Why are people fascinated by the center of something?

MILLER: Well, from what I gather it's that a center is a way for people to orient themselves on the face of the Earth. It's a way for people to sort of wrap their minds around where they stand. The neat thing about the centroid is that it's a sort of shorthand way of tracing the path and the growth of the American population across the landscape of the United States.

So back during the first decennial census in 1790, the centroid marker was placed just outside of Baltimore. And that makes sense because most of the American population at that time was concentrated on the eastern seaboard.

GREENE: There was no weight out West to move the center of that direction.

MILLER: No weight. Yeah. So the balance point was far east. But in the 220 years of the growth of the country this point has migrated slowly, you know, across the West Virginia Highlands, across Ohio, Indiana and Illinois, and into this point in Missouri. And what that tells you is the story of westward migration.

One interesting thing is that around 1920, 1930 this center point began to shift southward. And I was puzzled why this happened, and the big reason is air conditioning.


MILLER: You had these big hydroelectric projects in the Southwest and southern United States that powered these big cities that allowed population growth into these warmer climes.

GREENE: And another thing that struck me, I mean, there's so much whimsy here. I mean, you visited some of these places and you show up in these random spots and meet these interesting people. And I was struck by this visit to Edgar Springs, Missouri. That was the centroid in 2000. Tell me about the guy you met there.

MILLER: Yeah. The centroid marker happens to be set in the front yard of a fellow named Junior Harris.


GREENE: In his yard.

MILLER: In his yard. Yeah. And Dave was interested...

GREENE: Dave is one of the officials from the National Oceanic and Atmospheric Administration you travel with.

MILLER: Yeah. Dave Doyle. Yeah, the chief surveyor. And he asked Junior if he was aware of what the significance of the marker was, and Junior responded, well, yeah. If I step to the east side of my property, the whole world shifts.


MILLER: So he had become sort of an informal ambassador of this marker. And that's the great thing about following this path. I haven't visited every town where the centroid lands, but you can stitch together a nice little narrative about the growth and evolution of the country.

Another thing that I realized is this is very much a road narrative. You know, if you look at the map, the path of the centroid roughly follows the path of US 50.


MILLER: Which is the highway that runs from Ocean City, Maryland to Sacramento, California.


MILLER: And, you know, the growth of the United States is predicated on the growth of its road networks. You can sort of set out onto the road and weave together a nice little story about America itself.

GREENE: Interesting. Well, wherever the centroid goes, I am sure you'll be following it, Jeremy. Thanks for...

MILLER: I will.

GREENE: Thanks for talking to us about that.

MILLER: Thank you very much for having me. I appreciate it.

GREENE: It's reporter Jeremy Miller. His article "The Centroid: On the Road with the Population of a Restless Nation" appears in the latest edition from Orion Magazine. And he joined us from Berkeley, California.


GREENE: This is NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.