Northern Illinois Drift Plain

Northern Illinois Drift Plain. The Northern Illinois Drift Plain is a major physiographic region encompassing much of northern Illinois, characterized by its flat to gently rolling terrain formed by ancient glacial activity. It is a classic example of a till plain, composed of thick deposits of glacial drift left by the retreating Laurentide Ice Sheet. This fertile and geologically young landscape has profoundly influenced the region's agricultural development, hydrology, and human settlement patterns from pre-Columbian times to the present.

Geography and Geology

The region is bounded roughly by the Illinois River to the west and south, transitions into the Bloomington Ridged Plain further south, and shares a border with the distinct Wisconsin Driftless Area to the northwest. Its topography is primarily a product of the Wisconsin glaciation, specifically the advances of the Lake Michigan Lobe and the Green Bay Lobe. The underlying bedrock, primarily Silurian dolomite and Ordovician shale, is buried deep beneath unconsolidated glacial deposits including ground moraine, end moraine, and extensive outwash plains. Notable surface features include low, broad moraines such as the Marengo Moraine and the Valparaiso Moraine, as well as isolated kames and eskers. The region's highest natural point, Charles Mound, is a kame located near the border with Wisconsin.

Climate and Hydrology

The area experiences a humid continental climate, characterized by hot, humid summers and cold, snowy winters, influenced by air masses from the Gulf of Mexico and the Canadian Prairies. Precipitation is relatively evenly distributed throughout the year. The hydrology is dominated by a dendritic network of streams and rivers that flow westward into the Mississippi River system. Major waterways dissecting the plain include the Rock River, the Kishwaukee River, the Pecatonica River, and the Fox River. Much of the original pre-settlement hydrology has been altered by extensive drainage tile systems installed to convert wetlands to farmland, significantly impacting the flow regimes of streams like Spoon River and Macoupin Creek.

Ecology and Biodiversity

Prior to European-American settlement, the region was a vast mosaic of tallgrass prairie, oak savanna, and wetlands, with forest corridors primarily confined to river valleys like those of the Kankakee River. This ecosystem supported high biodiversity, including keystone species like the American bison and predators such as the gray wolf. Remnant prairie preserves, such as Nachusa Grasslands and Goose Lake Prairie State Natural Area, protect fragments of this original vegetation. The wetlands, including the historically extensive Grand Prairie marshes, were critical habitats for migratory waterfowl along the Mississippi Flyway. Contemporary conservation efforts by organizations like The Nature Conservancy focus on restoring these native plant communities and associated fauna.

Land Use and Agriculture

The region is part of the Corn Belt and is overwhelmingly dominated by intensive row-crop agriculture, particularly the cultivation of corn and soybean. The deep, fertile soils, primarily Mollisols like Drummer silty clay loam, are among the most productive in the world, a direct result of the prairie biome and glacial parent material. This agricultural economy supports major grain processing and agribusiness centers, including DeKalb, home to the former DeKalb Agricultural Association. Livestock production, especially swine and cattle, is also significant. Urban and suburban development, radiating from the Chicago metropolitan area and cities like Rockford and Aurora, continues to convert agricultural land.

History and Settlement

The area was historically inhabited by Native American tribes, including the Illinois Confederation, Potawatomi, and Sauk, who utilized the prairie and riverine resources. Early European exploration and trade was influenced by figures like Jacques Marquette and Louis Jolliet. Following the Black Hawk War and subsequent treaties like the Treaty of Chicago, American settlement accelerated in the 1830s, facilitated by infrastructure projects like the Illinois and Michigan Canal. The development of the steel plow by John Deere and the expansion of railroads, such as the Chicago and North Western Railway, transformed the prairie into an agricultural powerhouse. The region's growth is also tied to industrial cities like Elgin and the manufacturing legacy of Caterpillar Inc. in Peoria. Category:Regions of Illinois Category:Physiographic regions