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- United States. Congress--Records and correspondence 90
- Northwest, Pacific 85
- River engineering 75
- Bodies of water 39
- Rivers 39
- River surveys 31
- Harbors 23
- River channels 23
- Bridges--Design and construction 22
- Rapids 17
- West (U.S.) 17
- Canals 14
- United States--Armed Forces--Organization--Charts, diagrams, etc 10
- Photography 7
- Conservation of natural resources 3
- Renewable energy sources 3
- Riparian areas 3
- Transportation 3
- Agriculture 2
- Fisheries 2