Region
North America
86
United States
41
California
22
Alaska
20
Colorado
17
Montana
11
New Mexico
11
Nevada
10
Utah
9
West (U.S.)
9
New York (State)
8
Wyoming
8
Idaho
6
Pennsylvania
5
Texas
5
Arizona
4
Missouri
4
North Dakota
4
Oregon
4
Connecticut
3
Green River Formation
3
Kansas
3
Massachusetts
3
Minnesota
3
Vermont
3
Afghanistan
2
Albuquerque
2
Arkansas
2
Black Hills (S.D. and Wyo.)
2
Illinois
2
Maine
2
Middle Atlantic States
2
New Jersey
2
Ohio
2
Oklahoma
2
Pacific Coast (U.S.)
2
Rhode Island
2
San Juan River Watershed (Colo.-Utah)
2
South Dakota
2
Virginia
2
Washington (State)
2
Wisconsin
2
Absaroka-Beartooth Wilderness (Mont. and Wyo.)
1
Alabama
1
Alaska Peninsula
1
Alaska, Gulf of
1
America
1
Atlantic Coast
1
Atlantic States
1
Australia
1
more ...