Madison county is located in south central Iowa in the third tier of counties north of Missouri and the fourth tier east of the Missouri river. It is entirely within the southern Iowa loess area and hence the soils of the county are mainly loessial in origin. There is, however, a considerable acreage on which drift soils are mapped, these soils being derived from the glacial material of the Kansan drift. These drift soil areas are found where the covering of loess has been removed by erosion.