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Subject
- Roads34
- Harbors18
- Groundwater15
- United States. Congress. House15
- Geology, Stratigraphic12
- Election districts11
- Atlases10
- Stratigraphic correlation10
- Aquifers9
- Great Britain. Colonial Office9
- Water table7
- Coal5
- Geology5
- Census districts4
- Gravity anomalies4
- College graduates3
- Dioxane3
- Early maps3
- Hazardous waste sites3
- Historical geography3