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- Locks (Hydraulic engineering) 55
- Waterways 24
- Steamboats 21
- Rivers 14
- Boats and boating 10
- River engineering 10
- United States--Appropriations and expenditures 9
- Northwest, Pacific 8
- River boats 8
- River steamers 8
- Ships 8
- Canals--Design and construction--Costs 7
- Dams--Design and construction 6
- Passenger ships 6
- Rivers--Oregon 6
- West (U.S.) 6
- River surveys 5
- Bodies of water 4
- Photography 4
- Anniversaries 2
