S1, E1: The Mississippi River begins as a stream from Lake Itasca in Minnesota before gathering in size and power on its 2,300-mile journey south. Follow the first leg of its path, from the Upper Mississippi watershed to Minneapolis skyscrapers to the western Wisconsin border. Discover the wildlife that depends on the river to survive, from raccoons gearing up for the winter to black bears awaking at the first hints of spring to the massive swarm of mayflies that live a lifetime in a summer day.