Washington County is located in southeastern Iowa in the second tier of counties west of the Mississippi River and in the third tier north of the Missouri state line. It lies partly in the Mississippi loess and partly in the Southern Iowa loess soil areas and hence the soils are all of loessial origin.
Brown, P. E.; Orrben, C. L.; Meldrum, H. R.; and Englehorn, A. J., "Soil Survey of Iowa, Report No . 77—Washington County Soils" (1935). Soil Survey Reports. 75.