The John Wesley Powell expedition of 1869 explores the dangerous Colorado River, withstands internal dissension, and finally discovers the Grand Canyon.
| Actor | Role |
|---|---|
 Brian KeithWilliam Dunn | William Dunn |
 Ben JohnsonGeorge Bradley | George Bradley |
 John BealMaj. John Wesley Powell | Maj. John Wesley Powell |
 James DruryWalter Powell | Walter Powell |
 R.G. ArmstrongOramel Howland | Oramel Howland |
 L.Q. JonesBilly Hawkins | Billy Hawkins |
| DDan SheridanJack Sumner | Jack Sumner |
 Stan JonesSeneca Howland | Seneca Howland |
 David FrankhamFrank Goodman | Frank Goodman |
 Roy BarcroftJim Baker | Jim Baker |
 Jack Big HeadAshtishkel | Ashtishkel |
 Pat HoganIndian chief | Indian chief |
| DDawn Little SkyIndian woman | Indian woman |
 David StolleryAndrew 'Andy' Hall | Andrew 'Andy' Hall |
 Ray WalkerMcSpadden (uncredited) | McSpadden (uncredited) |