Region
United States
26
Mississippi River
6
Colorado
5
Mississippi River Valley
4
Missouri River
4
California
3
Great Britain
2
Northwestern States
2
Ohio River
2
Washington (D.C.)
2
Alaska
1
Biscayne Bay
1
Blockhouse Creek
1
Chicago Metropolitan Area
1
Colorado River (Colo.-Mexico)
1
Florida
1
Golden Gate National Recreation Area (Calif.)
1
Illinois
1
Maine
1
North America
1
Pennsylvania
1
Steam Valley Run
1
Utah
1
West (U.S.)
1
Wyoming
1