Trevor McDonald embarks on an epic 2,000 mile journey along the great Mississippi River to discover why it is the most important river in the United States. His journey begins in the Gulf of Mexico where the river flows into the sea, and ends at the river's source near the Canadian Border. Throughout his voyage, Trevor uncovers how the river has helped define America. In the Deep South he sees how the legacy of slavery still affects life along the river today and witnesses a colourful Jazz funeral in New Orleans. In Memphis, Trevor meets Rev. Kyles who was standing beside Dr. Martin Luther King when he was assassinated. He visits Hollywood star Morgan Freeman who reveals why he returned to his roots in Mississippi after forty years away. And Trevor's in for a surprise when he reaches his ultimate destination, the source of the Mississippi River.