Region
Texas
27
Oklahoma
6
Louisiana
4
New Mexico
4
Montana
3
Alaska
2
Fort Worth Basin
2
Ohio
2
Permian Basin (Tex. and N.M.)
2
United States
2
Van Zandt County
2
Wyoming
2
Alabama
1
Anderson County
1
Arizona
1
Austin County
1
Beaverhead County
1
Caddo Lake (La. and Tex.)
1
Caddo Parish
1
California
1
Carter County
1
Creek County
1
Cuyahoga County
1
Estill County
1
Fremont County
1
Gulf Coast
1
Idaho
1
Kentucky
1
Minnesota
1
Natrona County
1
North America
1
Norton Bay-Nulato region
1
Panola County
1
Pennsylvania
1
Seward Peninsula
1
Smith County
1
Stephens County
1
Teton County
1
Washington County
1
Weston County
1