Once a decade the United States Census Bureau marks a point on the nation's map that it calls the "National Mean Center of Population." The Census Bureau describes it as "the place where an imaginary, flat, weightless and rigid map of the United States would balance perfectly if all 308,745,538 residents counted in the 2010 Census were of identical weight." (Hat tip to NYT's Economix)
This decade's National Mean Center of Population in Plato, Missouri maintains the steady westward movement that the point has made since it first started in 1790 in Kent County, Maryland. As people travelled westward, the national mean center crawled after them. This decade's step of 23.4 miles West and slightly South marks the shortest distance the point has travelled since 1970.