Kaskaskia River Basin.—The Kaskaskia River is also known as the Okaw. It rises in Champaign County where the watersheds of the Wabash, Kaskaskia, and Illinois basins meet. The river flows southwestward and joins the Mississippi in Randolph County.
Shelbyville and Vandalia arc located on the Kaskaskia River; Hillsboro is on Shoal Creek, the most important western tributary; and Centralia on Crooked Creek, the principal eastern tributary. Belleville and Waterloo are on the divide between the Kaskaskia and Mississippi.
The basin of the Kaskaskia is about 190 miles in length, but the river, which is very crooked, has a length of nearly 400 miles. The average width of the basin is 30 miles and its extreme width about 60 miles. Its area is 5,710 square miles. The basin lies in the Lower Illinoisan, Middle Illinoisan, and Early Wisconsin glaciations. Swamp and overflow lands are common in the valley of the river. The surface of the basin is decidedly level, varied somewhat by the stream valleys, kames, and moraines. A group of glacial ridges known as kames extends from Jackson and Randolph counties through St. Clair County and on to Tower Hill in Shelby County. They are long, narrow ridges or smaller knolls rising abruptly from the level plain to heights of 75 to 130 feet. Their distribu tion is well shown on the soil map.
The Shelbyville moraine is the outer margin of the Wis consin glaciation. It extends from Indiana westward across Illinois to Shelbyville, the city which has given its name to the moraine. Here the moraine turns abruptly northward. In Peoria County it is overridden by the Bloomington moraine formed at a later stage of the Early Wisconsin glaciation. The Shelbyville moraine rises GO to 100 feet above the level lands of the Illinoisan glaciation. It forms a striking feature in the landscape when seen from the south, but it passes more gradually into the level ground moraine to the north. The moraine is cut by the Kaskaskia at Shelbyville. Southward from the Shelbyville bridge the valley presents the character istics of a broad, well-matured valley, while northward it appears much younger. The two drift sheets in which the
valley lies differ widely in age and topography, thus giving a sudden change to the appearance of the stream valley.
The Kaskaskia Valley is of historic note as it contains the site of the earliest permanent Illinois settlement and is the seat of the first two capital cities of the state.
Big Muddy River Basin.—The Big Muddy River flows along the eastern and southern parts of its basin; the Little Muddy along the center; and Beaucoup Creek along the western part. The basin is somewhat elliptical in shape with its axes about 70 miles and 50 miles in length. The area is 2,230 square miles. Most of the surface is level except for the numerous shallow trenches cut by the streams. In the southern part of the basin, however, the topography changes rapidly from the level plains of the Illinois glaciation to the rugged lands of the Illinois Ozarks. The traveler whose impressions of Illinois topography have been gained from journeys in the central part of the state will find unexpected variety in a journey of only a few miles southward from Carbondale among the narrow defiles and precipitous cliffs of Bosky Dell and Makanda.
Rich coal deposits underlie the basin of the Big Muddy, and the mines of this region are among the most productive of the state. A number of important cities are found within the basin. In the eastern part are Mount Vernon, Benton, Johnston City, and Marion; in the southern portion Herrin, Carterville, Carbondale, and Murphysboro; in the northwest Duquoin and Pinckneyville.
Minor basins of the Mississippi.—Areas of considerable extent are a part of the Mississippi Basin, hut arc not included in the basins already described. These lie along the western edge of the state, including nearly all the Illinois bluffs of the Mississippi with triangular-shaped areas extending eastward from 10 to 50 miles. They include much of the most rugged and most picturesque scenery of the state. The immediate bluffs rise to heights of 100, 200, and 300 feet, or more, above the flood plain of the Mississippi.