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- Bodies of water 29
- Rivers 29
- United States. Congress--Records and correspondence 29
- River engineering 28
- River surveys 26
- River channels 22
- Harbors 19
- Northwest, Pacific 17
- West (U.S.) 13
- Canals 12
- Rapids 10
- United States--Armed Forces--Organization--Charts, diagrams, etc 9
- Bridges--Design and construction 6
- Agriculture 1
- Conservation of natural resources 1
- Fisheries 1
- Forests and forestry 1
- Irrigation projects 1
- Maps 1
- Mineral industries 1