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- Canals 30
- Rivers 24
- River engineering 19
- Bodies of water 18
- Northwest, Pacific 17
- United States. Congress--Records and correspondence 17
- River surveys 15
- River channels 13
- Rapids 11
- Photography 10
- United States--Armed Forces--Organization--Charts, diagrams, etc 10
- West (U.S.) 9
- Explorers 7
- Harbors 7
- Bridges--Design and construction 5
- Inland navigation 4
- Discoveries in geography 3
- Commerce 2
- Dams--Surveying 2
- Steamboats 2