The Mississippi River is an American icon. It's a body of water that’s been shaped as much by cultural processes as by environmental ones. From the state lines it draws to its role in literature and the arts, it’s a river that flows deep in the American psyche. This episode is about the boundaries and horizons of the Mississippi — its deep geologic past, its history as a route to freedom, and its meaning today.  A Hawk and a Warbler; When The Mississippi Met the Atlantic; Life on Mark Twain's Mississippi; The Music and Meaning of Sounding 'Mark Twain'; Boundary and Horizon: The Mississippi River in African-American History.