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Topic
- West (U.S.) 217
- Bodies of water 159
- River engineering 122
- Northwest, Pacific 107
- Rivers 99
- Railroad engineering 50
- Explorers 46
- Canals--Design and construction--Costs 38
- United States--Appropriations and expenditures 36
- Transportation 34
- Dams--Design and construction 32
- Discovery and exploration 30
- Water resources development 30
- Photography 27
- River surveys 17
- United States. Congress--Records and correspondence 15
- Harbors 13
- River channels 10
- Canals 9
- Rapids 8
