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- Bodies of water 9
- Rivers 9
- River engineering 7
- United States. Congress--Records and correspondence 7
- River channels 6
- River surveys 6
- West (U.S.) 6
- Harbors 5
- Northwest, Pacific 4
- Conservation of natural resources 3
- Water resources development 3
- Water-power 3
- Canals 2
- Fisheries 2
- Maps 2
- Wildlife conservation 2
- Agriculture 1
- Bridges--Design and construction 1
- Forests and forestry 1
- Hydroelectric power plants 1