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Topic
- West (U.S.) 210
- Bodies of water 153
- River engineering 118
- Northwest, Pacific 104
- Rivers 94
- Railroad engineering 48
- Explorers 46
- Canals--Design and construction--Costs 35
- United States--Appropriations and expenditures 35
- Transportation 31
- Discovery and exploration 30
- Dams--Design and construction 29
- Water resources development 28
- Photography 27
- River surveys 14
- United States. Congress--Records and correspondence 13
- Harbors 11
- River channels 10
- Canals 9
- Inland navigation 6
