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- West (U.S.) 38
- Transportation 32
- United States--Appropriations and expenditures 32
- River engineering 31
- Canals--Design and construction--Costs 30
- Dams--Design and construction 29
- Bodies of water 27
- Northwest, Pacific 25
- Rivers 25
- Water resources development 25
- River surveys 17
- United States. Congress--Records and correspondence 7
- Locks (Hydraulic engineering) 4
- Railroad engineering 2
- Bridges--Design and construction 1
- Cascade Range 1
- Military maps 1
- Military topography 1
- Railroad construction & maintenance 1