Carroll County is located in west central Iowa in the third tier of counties east of the Missouri River and in the center tier of counties north and south. It is partly in the Wisconsin drift soil area and partly in the Missouri loess soil area, and hence the soils of the county are partly of loessial and partly of drift origin.
Stevenson, W. H. and Brown, P. E., "Soil Survey of Iowa, Report No. 60—Carroll County Soils" (1930). Soil Survey Reports. 60.