Region
Colorado
330
California
316
Utah
245
Wyoming
240
Montana
201
Nevada
201
Alaska
169
Arizona
160
New Mexico
153
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
45
North America
43
Wisconsin
43
Middle West
41
Illinois
37
Oregon
36
North Dakota
34
San Juan Basin (N.M. and Colo.)
34
Oklahoma
33
Pennsylvania
33
Florida
32
New Jersey
32
Missouri
31
Green River Formation
30
Uinta Basin (Utah and Colo.)
29
Colorado Plateau
28
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
Southern States
22
Arkansas
21
New England
21
China
20
Massachusetts
20
Puerto Rico
20
more ...