The song is a traditional Amercian folk song of unknown origin.
It is also known as "Oh Shenandoah" or "Across the Wide Missouri"
Recordings of the song have been made by among others Bing Crosby, Harry Belafonte, Bob Dylan, Judy Garland and Bruce Springsteen
Modern romantic jazz sheet music arrangement which can be used as lead sheet (including chords) by Lars Christian Lundholm