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Topic
- Rivers--Oregon 47
- Dams 30
- Water--Pollution 20
- Flood control 16
- Lectures and lecturing 14
- Fishes--Conservation 13
- Salmon 13
- Sewage disposal plants 5
- Inland water transportation 4
- Izaak Walton League of America 4
- Conservation--Law and legislation 2
- Fishing 2
- Irrigation 2
- Oregon Audubon Society 2
- Roads 2
- Antelopes 1
- Bears 1
- Beebe, William, 1877-1962 1
- Birdhouses 1
- Conservation of natural resources 1