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Topic
- River engineering 63
- Northwest, Pacific 56
- United States. Congress--Records and correspondence 53
- Bodies of water 41
- River surveys 34
- Rivers 34
- Harbors 33
- River channels 22
- West (U.S.) 20
- United States--Appropriations and expenditures 14
- Rapids 13
- Canals 12
- United States--Armed Forces--Organization--Charts, diagrams, etc 11
- Water-power 11
- Maps 9
- Photography 8
- Agriculture 7
- Conservation of natural resources 7
- Bridges--Design and construction 6
- Riparian areas 6