Region
Colorado River (Colo.-Mexico)
8
Grand Canyon (Ariz.)
Arizona
5
Grand Canyon
5
Colorado River
4
North America
4
Colorado River Valley (Colo.-Mexico)
3
Colorado Plateau
2
Green River (Wyo.-Utah)
2
West (U.S.)
2
Colorado River Valley
1
Grand Canyon National Park (Ariz.)
1
United States, West
1
West United States
1