Region
United States
6
Mississippi River Valley
3
Ohio River Valley
3
Colorado River
2
Colorado River (Colo.-Mexico)
2
Colorado River Valley
2
États-Unis
2
North America
2
Southwest, New
2
California, Southern
1
Colorado (Col.-Mexique : Fleuve)
1
Colorado River Valley (Colo.-Mexico)
1
États-Unis (Nouveau Sud-Ouest)
1
États-Unis (Ouest)
1
Mississippi, Vallée du
1
New Southwest
1
Ohio, Vallée de l'
1
Southern California
1
West (U.S.)
1
West United States
1