Region
United States
21
Great Plains
3
Colorado
2
England
2
Illinois
2
Southern States
2
West (U.S.)
2
Cahokia Mounds State Historic Park
1
California
1
Calixtlahuaca
1
Calixtlahuaca (Mexico)
1
Chesapeake and Ohio Canal National Historical Park
1
Concord (Mass.)
1
Concord Region
1
Durango
1
Durango (Colo.)
1
France
1
High Plains (U.S.)
1
India
1
Maryland
1
Massachusetts
1
Mexico
1
Missouri
1
New Jersey
1
Ogallala Aquifer
1
Russia
1
Saint Louis County
1
Saint Louis County (Mo.)
1
Sandwich
1
Sandwich (Ill.)
1
South Dakota
1
Southwestern States
1
Tennessee
1
Texas
1
Ulysses S. Grant National Historic Site (Mo.)
1