With many collisions and much crumpling of rock, down the ages. The story holds lessons for how the edges of continents are built and change over time.

Earthworks built around 3,700 years ago in Louisiana centered an exchange system that stretched up the Mississippi and into the Ohio and Tennessee Valleys.

From 1857 to 1889, he could be found walking a 365-mile loop in western Connecticut and eastern New York. Everybody recognized him, but no one knew his name.