1. New England

2. Mid-Atlantic

3. South Atlantic-Gulf

4. Great Lakes

5. Ohio

6. Tennessee

7. Upper Mississippi

8. Lower Mississippi

9. Souris-Red-Rainy

10. Missouri

11. Arkansas-White-Red

12. Texas-Gulf

13. Rio Grande

14. Upper Colorado

15. Lower Colorado

16. Great Basin

17. Pacific Northwest

18. California

19. Alaska

20. Hawaii