Topography of Cook County

The landforms of Cook County are mostly the result of depositional glacial processes. The significant topographic features include broad, almost level plains that were once lake beds; concentric, subparallel ridges formed as moraines, marking the outer margins of continental glaciers. Gentle, elongate sandy spits, bars, and beach ridges formed along the shore of glacial Lake Chicago and other ancestors of present-day Lake Michigan.

The highest point in Cook County is at the northwest corner and is almost 1,000 feet above sea level. For most of the county, the topography slopes gradually toward Lake Michigan to the east and is dissected by north-south trending stream-cut valleys. Most of the central and southeastern portion of Cook County is composed of a low, flat plain.

Updated 10/23/2009 SLD