Winnebago county is located in northern central Iowa, bordering on the state of Minnesota, and almost in the exact center of the northern boundary of the state. It lies entirely within the Wisconsin drift soil area. Hence the upland soils of the county are all of glacial origin and the terrace and bottomland types also are derived from the drift material.
Stevenson, W. H. and Brown, P. E., "Soil Survey of Iowa, Report No. 23—Winnebago County Soils" (1922). Soil Survey Reports. 29.