Region
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Black Hills
12
Carbon County
12
Front Range (Colo. and Wyo.)
12
Grand Canyon (Ariz.)
12
Gulf Coast (U.S.)
12
India
12
Iowa
12
Kern County
12
New England
12
Northeastern States
12
Piceance Creek Basin
12
Sweetwater County
12
Asia
11
Cochise County
11
Middle Atlantic States
11
National Petroleum Reserve (Alaska)
11
Seward Peninsula
11
Uinta Basin
11
Washington County
11
Custer County
10
Indiana
10
Johnson County
10
Lander County
10
Minas Gerais (Brazil)
10
Mississippi River Valley
10
Nye County
10
Park County
10
Russia (Federation)
10
San Juan Mountains (Colo. and N.M.)
10
Santa Maria Basin
10
Arctic Ocean
9
Atlantic Coast (U.S.)
9
Baja California (Peninsula)
9
Bighorn Basin (Mont. and Wyo.)
9
Brooks Range
9
Clark County
9
Clear Creek County
9
Colorado River (Colo.-Mexico)
9
Gulf States
9
Middle East
9
Mohave County
9
Moon
9
National Petroleum Reserve
9
New Madrid Region
9
North Slope (Alaska)
9
Piedmont (U.S. : Region)
9
Powder River Basin
9
San Francisco Bay Area
9
San Juan Basin
9
Saudi Arabia
9
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