ABSTRACT: The Kankakee River lowland is an intermorainic trough bounded by the Valparaiso Moraine on the north and the Iroquois Moraine on the south. It consists of three principal terrains: (1) the Kankakee River floodplain; (2) the Fair Oaks eolian plain; and (3) the Knox lowland between the northeast terminus of the Iroquois Moraine and the Maxinkuckee Moraine to the east. The sediments of the Kankakee River lowland are divided into four assemblages based on areal distribution, stratigraphic relationships, and genetic associations. They include: (1) alluvial and eolian sands, organic mud and sand, and peat of the Kankakee-Valparaiso assemblage; (2) till, lacustrine mud, and minor sand and gravel of the Snider assemblage; (3) basal and ablation till, and sand and gravel of the Trafalgar assemblage; and (4) a heterogenous group of sediments grouped into a pre-Snider assemblage, except where the occurrence of distinctive lithologies allows a more detailed stratigraphic definition. The principal aquifer in the Kankakee River lowland is the fluvial and eolian sands of the Kankakee-Valparaiso assemblage that occur at or near the surface throughout the lowland. Sand and gravel bodies in the pre-Snider Assemblage occur in bedrock valleys under the lowland, and small scattered bodies of sand and gravel in the Trafalgar and Snider assemblages of the Iroquois Moraine may also serve as aquifers.