Region
California
68
Colorado
47
Alaska
32
Wyoming
31
Nevada
26
Utah
21
Arizona
16
North America
16
New Mexico
15
Washington (State)
14
Mexico
12
Baja California (Peninsula)
11
Montana
11
Panama
11
Piceance Creek Basin
11
Texas
11
United States
11
Canal Zone
10
Oregon
10
Puerto Rico
10
West (U.S.)
9
Southern States
8
Uinta Basin (Utah and Colo.)
8
Fremont County
6
Maryland
6
New Jersey
6
Olympic Peninsula
6
Virginia
6
Florida
5
Inyo County
5
Natrona County
5
San Joaquin Valley
5
Atlantic States
4
California, Southern
4
Coast Ranges
4
Japan
4
Kootznahoo Formation (Alaska)
4
Lincoln County
4
Mississippi Embayment
4
North Carolina
4
Nye County
4
San Juan Basin (N.M. and Colo.)
4
South Carolina
4
Cook Inlet Region
3
Georgia
3
Green River Formation
3
Mays Landing Region
3
North Slope
3
Okinawa-ken
3
Piceance Creek Basin (Colo.)
3
more ...