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- West (U.S.) 180
- Bodies of water 140
- Northwest, Pacific 104
- River engineering 95
- Rivers 81
- Railroad engineering 48
- Explorers 45
- Canals--Design and construction--Costs 35
- Transportation 31
- Dams--Design and construction 29
- Discovery and exploration 29
- Water resources development 28
- Photography 25
- United States--Appropriations and expenditures 22
- Canals 5
- Inland navigation 5
- Locks (Hydraulic engineering) 5
- Salmon 3
- Boats and boating 2
- Railroads 2
