Poweshiek County is located in southeastern Iowa in the fourth tier of counties north of Missouri and in the fifth tier west of the Mississippi River. It is partly in the Mississippi loess and partly in the Southern Iowa loess soil areas and hence the soils are mainly of loessial origin, only small areas of drift soils being exposed where the loessial covering has been removed by erosion.
Brown, P. E.; Benton, T. H.; Meldrum, H. R.; and Englehorn, A. J., "Soil Survey of Iowa, Report No. 74—Poweshiek County Soils" (1935). Soil Survey Reports. 78.