Region
Colorado
330
California
318
Utah
248
Wyoming
240
Nevada
202
Montana
201
Alaska
170
Arizona
160
New Mexico
154
Texas
136
Idaho
119
United States
109
Kansas
79
West (U.S.)
70
Michigan
69
Powder River Basin (Wyo. and Mont.)
69
Washington (State)
55
Virginia
54
Kentucky
46
North America
44
Wisconsin
43
Middle West
41
Illinois
37
Oregon
36
San Juan Basin (N.M. and Colo.)
35
North Dakota
34
Oklahoma
33
Pennsylvania
33
Florida
32
New Jersey
32
Missouri
31
Green River Formation
30
Uinta Basin (Utah and Colo.)
30
Colorado Plateau
29
Minnesota
28
North Carolina
28
Piceance Creek Basin
28
South Dakota
27
Georgia
25
New York (State)
25
Phosphoria Formation
25
South Carolina
24
Appalachian Basin
23
Mexico
23
New England
22
Southern States
22
Arkansas
21
Massachusetts
21
China
20
Puerto Rico
20
more ...