This is from an episode of "The Johnny Cash Show", which aired on the ABC network from 1969-1971. You will find a clip from Johnny Cash's TV show on which Pete Seeger talks about his friend from Florida, Will McLean and then does "Osceola."

This clip features Johnny Cash and legendary folk singer Pete Seeger singing songs including "Cripple Creek" and "Worried Man Blues". Cash fought for a year to have Seeger on his show, despite the reluctance of the network executives. (Seeger was known for his political outspokenness). This episode aired on March 4th, 1970.