The river that rises in the Rockies and flows into the Gulf of California

1. Colorado
2. Mississippi
3. St. Lawrence
4. Mack

Isthmus of Panama connects North America to South America in the

1. East
2. South
3. West
4. North

The major drainage system of North America with river Ohio as its major tributary

1. Mississippi
2. Colorado
3. St. Lawrence
4. Mackenzie

Niagara Falls is on this river

1. St. Lawrence
2. Mississippi
3. Mackenzie
4. Colorado