An amazing & interactive chart showing the U.S. population center for the last two centuries

This is a pretty masterful interactive chart showing the center of population of the United States for the last 220 years--fascinating, and just maybe, an example of the far reach and influence of the information visionary Edward Tufte?  The center of population "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."

---o0o---