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- River engineering 91
- West (U.S.) 80
- Bodies of water 79
- Northwest, Pacific 77
- Railroad engineering 49
- United States--Appropriations and expenditures 15
- River surveys 9
- Transportation 5
- Canals--Design and construction--Costs 4
- Dams--Design and construction 3
- United States. Congress--Records and correspondence 3
- Locks (Hydraulic engineering) 2
- Railroad construction & maintenance 2
- Bridges--Design and construction 1
- Cascade Range 1
- Military maps 1
- Military topography 1
- Railroads--Design and construction 1
- Rivers 1