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Topic
- Discovery and exploration 3
- Explorers 3
- Canals--Design and construction--Costs 2
- Drawbridges 2
- Locks (Hydraulic engineering) 2
- Railroad engineering 2
- River engineering 2
- Rocks 2
- Steamboats 2
- United States--Appropriations and expenditures 2
- West (U.S.) 2
- Bodies of water 1
- Bridges 1
- Canals 1
- Carriages and carts 1
- Cities and towns 1
- Cliffs 1
- Columbia River 1
- Ferries 1
- Fishing 1