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- River engineering 30
- Rivers 30
- Bodies of water 29
- United States. Congress--Records and correspondence 28
- River surveys 27
- River channels 22
- Harbors 19
- Northwest, Pacific 17
- Canals 12
- West (U.S.) 12
- Rapids 10
- United States--Armed Forces--Organization--Charts, diagrams, etc 9
- Bridges--Design and construction 6
- Conservation of natural resources 1
- Maps 1
- Salmon fisheries 1
- Salmon 1
- Water resources development 1
- Water-power 1
- Watershed management 1