Subject Region
United States
19
West (U.S.)
7
Europe
4
Africa, East
3
Australia
3
Chesapeake Bay Watershed
2
Costa Rica
2
India
2
Kenya
2
New Mexico
2
Romania
2
Southern States
2
White Sands Missile Range
2
White Sands Missile Range (N.M.)
2
Africa
1
Alberta
1
Alberta, Northern
1
Arizona
1
Asia
1
Athabasca Tar Sands (Alta.)
1
California
1
Canada
1
European Union countries
1
Ganges River (India and Bangladesh)
1
Great Basin
1
Great Britain
1
Hawaii
1
Island County
1
Island County (Wash.)
1
Lehigh County
1
Lehigh River Valley
1
Nevada
1
Nevada National Security Site
1
New Zealand
1
North America
1
Northampton County
1
Oregon
1
Pennsylvania
1
Scandinavia
1
Tanzania
1
Washington (State)
1
West (United States)
1
Wyoming
1