Sac County is located in the northwestern part of Iowa, in the fourth tier of counties south of the Minnesota state line and in the third tier east of the Missouri River. It is partly in the Wisconsin drift soil area and partly in the Missouri loess area. The soils of the county are partly of glacial and partly of loessial origin.
Brown, P. E.; Orrben, C. L.; Meldrum, H. R.; and Bennett, R. E., "Soil Survey of Iowa, Report No. 71—Sac County Soils" (1933). Soil Survey Reports. 81.