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Subject
- Railroads14
- Indians of North America8
- Discovery and exploration4
- Discoveries in geography3
- American2
- Faults (Geology)2
- Gold mines and mining2
- Pacific railroads2
- Trails2
- AZ.1
- CA.1
- CO.1
- Cattle trails1
- Earthquakes1
- Explorations and surveys1
- Forest reserves1
- Forests and forestry1
- Frontier and pioneer life1
- Geothermal resources1
- Gold discoveries1
