Region
United States
255
Colorado
83
South Platte River Valley (Colo. and Neb.)
23
West (U.S.)
17
Antarctica
7
California
7
China
7
Great Lakes (North America)
5
North Atlantic Ocean
5
Polar regions
5
Rocky Mountains Region
5
Arctic regions
4
Developing countries
4
Europe
4
European Union countries
4
India
4
New Mexico
4
North Pacific Ocean
4
Northwest, Pacific
4
Arizona
3
Asia, Central
3
Brazil
3
Chesapeake Bay (Md. and Va.)
3
Colorado River Watershed (Colo.-Mexico)
3
Espanola Valley
3
Europe, Eastern
3
Florida
3
Germany
3
Latin America
3
Mexico
3
Mexico, Gulf of
3
Pacific Coast (U.S.)
3
Russia (Federation)
3
Southern States
3
Utah
3
Africa
2
Africa, Sub-Saharan
2
Arkansas River Watershed
2
Asia
2
Balkan Peninsula
2
British Columbia
2
Canada
2
East (U.S.)
2
East Asia
2
Europe, Central
2
Front Range (Colo. and Wyo.)
2
Jupiter (Planet)
2
Korea (South)
2
Mars (Planet)
2
Middle East
2
more ...