Where's the geographic center of the "lower 48" states? Everyone knows it's in Kansas. But there are other kinds of centers...
When Jay told me the other night that he was from central NJ and I asked if that was near Trenton, he told me Trenton is in southern NJ. Then why is Trenton right on the crease in my road atlas where the two pages of the NJ map meet? Evidently Jay was thinking about a different kind of "space" than simple geography - he was thinking of population. It's certainly true that Trenton is well south of most of the population of NJ, even if it's dead center geographically.
That got us wondering... where's the "population center" of the lower 48? And how about the "elevation center"? The "agricultural center"? The "black center"?
Each of these centers is a kind of balancing point. Picture a piece of cardboard cut out in the shape of the lower 48 states. If it's just the cardboard, you could balance it on your fingertip by putting your finger under the geographic center (if you didn't sneeze). But if you put, say, pennies on the cardboard in proportion to the population at each point around the country, you can imagine it wouldn't balance at the same point - you'd need to move your finger to the "population center" to do that. If you added plaster on top of the cardboard shaped like the mountains and valleys of the country, it would balance in a different place again, the "elevation center". So, can you figure out which center is which in the map below? There are two hints below if you need help...
Hint 1: the light blue and red background is a map of the population density on a county-by-county basis.
Hint 2: you already know that the geographic center is in Kansas, and some of the other markers have colors that might suggest which center they are.
Ok... just to make sure there's no confusion: white=geographic; red=total population (who was it that guessed Ohio?); orange=elevation; green=cropland; black=black population. Population data are from 1997; crop data from 1987; elevation data from GTOPO30. The county and state geographic data sets (and the population data) came with the ArcView software distributed by ESRI.