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- Transportation 15
- Bodies of water 14
- Canals--Design and construction--Costs 14
- Dams--Design and construction 14
- West (U.S.) 14
- Northwest, Pacific 13
- Rivers 13
- Water resources development 13
- River engineering 2
- River surveys 2
- United States--Appropriations and expenditures 2
- Cascade Range 1
- Locks (Hydraulic engineering) 1
- Military maps 1
- Military topography 1
- Railroad engineering 1
- United States. Congress--Records and correspondence 1