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Topic
- Bodies of water 20
- River channels 20
- River engineering 20
- Rivers 20
- United States. Congress--Records and correspondence 20
- River surveys 19
- Harbors 13
- Canals 11
- Northwest, Pacific 11
- West (U.S.) 9
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Region
- Columbia River >> Douglas County >> Washington >> United States 20
- Snake River >> Franklin County >> Washington >> United States 20
- Willamette River >> Multnomah County >> Oregon >> United States 20
- Oregon >> United States 19
- Washington >> United States 19
- Coos Bay >> Coos County >> Oregon >> United States 12
- California >> United States 7
- Clearwater River >> Nez Perce County >> Idaho >> United States 6
- Idaho >> United States 6
- Cowlitz River >> Cowlitz County >> Washington >> United States 4
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Institution
- University of Oregon 20