Subject
Iowa Description and travel
22
Iowa
12
Iowa History
9
Railroads
9
Floods
7
Frontier and pioneer life
6
Iowa Boundaries
6
Missouri Boundaries
6
Water quality
6
Hydrology
4
Groundwater
3
Older people Care
3
Streamflow
3
United States History Regimental histories
3
Water resources development
3
Wisconsin Description and travel
3
Agricultural chemicals Environmental aspects
2
Agricultural credit
2
Drift
2
Geomagnetism
2
Glacial epoch
2
Groundwater flow
2
Iowa Politics and government
2
Latter Day Saints
2
Nebraska Description and travel
2
Pacific railroads
2
Pavements, Concrete Maintenance and repair Evaluation
2
Public lands
2
Railroad land grants
2
Rain and rainfall
2
Rural development
2
Rural health services
2
Volunteer workers in social service
2
Water quality management
2
Accidents
1
Aeronautics, Commercial
1
Agricultural administration
1
Agriculture
1
Agriculture Environmental aspects Research
1
Argon-argon dating
1
Atrazine
1
Baptists
1
Biomass energy industries
1
Cedar Rapids (Iowa)
1
Cedar Rapids (Iowa) History
1
Cedar River Watershed (Minn. and Iowa)
1
Chemical plants Accidents
1
Chemicals Accidents
1
Chicago (Ill.) Description and travel
1
Child care services Finance
1
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