Region
Abbotsford
1
Aberdeen Proving Ground
3
Abū Ẓaby (United Arab Emirates)
1
Accomack County
1
Adirondack Mountains
1
Afghanistan
5
Africa
1
Africa, West
2
Alabama
15
Alameda County
1
Alamosa River Watershed
1
Alaska
14
Alaska Maritime National Wildlife Refuge (Alaska)
1
Alaska, Gulf of
1
Albany
2
Albany Region
1
Alberta
3
Alberta, Northern
1
Albuquerque
2
Algeria
1
Alps
1
Anacostia River (Md. and Washington, D.C.)
2
Anchorage
1
Anhui Sheng
1
Animas River (Colo. and N.M.)
4
Animas River Watershed
1
Animas River Watershed (Colo. and N.M.)
6
Antarctica
1
Apache County
1
Apalachicola River
1
Appalachian Region
10
Aral Sea (Uzbekistan and Kazakhstan)
1
Arctic regions
7
Ardmore
1
Arecibo
1
Arizona
11
Arkansas
3
Arkansas City
1
Arkansas River
1
Arkansas River Valley
1
Arkansas River Watershed
1
Arnold Air Force Base
1
Arnold Air Force Base Region
1
Ashland
1
Asia
1
Athabasca River
1
Athabasca River Watershed
1
Athabasca River Watershed (Alta.)
1
Athabasca Tar Sands (Alta.)
2
Atlanta
1
more ...