West Virginia was once the population center of the United States. For four decades. That's according to this awesome map -- built into an animation by Philip Bump -- from the Census Bureau that details the mean center of population for every decade from 1790-2010.  What's the "mean center"?  "The center is determined as the place where an imaginary, flat, weightless and rigid map of the United States would balance perfectly if all residents were of identical weight," explains the Census site.

Image courtesy of Census.gov

The current center of the country is Plato, Missouri, a town of 109 people, according to the 2010 census. That's the fourth straight decade that the center of the U.S. population has been in the Show Me State. The current population center is roughly 872 miles from Chestertown, Maryland, the center of the population in 1790. Want to take a more in depth look at the westward (and southward) movement of the U.S. population? The Census Bureau has you covered there, too.  Check out this map.