The Lit tle Wabash rises near Mattoon and flows southward nearly parallel with the Embarras, about 25 miles farther west. It joins the Wabash between White and Gallatin counties 15 miles above the Ohio. Skillet Fork is an impor tant western tributary of the Little Wabash. Effingham, Louisville, and Carmi are on or near the Little Wabash. Olney and Fairfield arc on tributaries.
The Wabash River Basin in Illinois occupies portions of the Early Wisconsin and Lower Illinoisan glaciations. The surface features of the northern portion consist of the level ground moraines of the Early Wisconsin, varied by numerous ridges of the Bloomington, Champaign, and Shelbyville terminal moraines. The topography of the southern portion is exceed ingly flat throughout as there is but slight development of moraines. In extensive areas not a knoll as much as 10 feet in height is to be found. This general flatness is interrupted, however, by the broad, shallow trenches of well-developed stream valleys. The bluffs and flood plain of the Wabash are important topographic features of this part of Illinois.
Ohio River Basin.—That part of Illinois which drains directly into the Ohio has an area of 2,730 square miles, and it cont ains the most rugged topography of the state, the Illinois Ozarks.
The Saline River and its tributaries reach northward in the level Lower Illinoisan glaciation to Hamilton County and southward to the crest of the Ozarks. Its basin has an area of 1,130 square miles. Harrisburg and Eldorado are in one of the most productive coal regions of the state.
Cache Valley, once occupied by the Ohio River, extends between two highland areas across Pope County, along the edges of Johnson, Union, Massac, Pulaski, and Alexander counties, and unites with the flood plains of both the Mississippi and Ohio. The eastern end of the valley is drained by Big Bay Creek, which rises in Johnson County and flows eastward across Pope County to the Ohio. Its basin has an area of 275 square miles. The larger part of the valley is drained by Cache River, which rises in the highlands to the north; enters the valley in Massac County; flows westward and south ward, joining the Ohio between Mound City and Cairo. The basin of the Cache River has an area of 623 square miles.
The divide between Big Bay Creek and Cache River lies in the swamp and overflow lands of the Cache Valley. So slight is this divide that a deep ditch in Big Bay Creek has been extended westward far enough to reverse a part of the natural drainage of the Cache River system.
The Ohio River is an important transportation route. The county seats of the six Illinois counties along the 126 miles of the Ohio are all river ports. These are Shawnee
town, Elizabethtown, Golconda, Metropolis, Mound City, and Cairo.
Rugged areas of Illinois.—Although Illinois is characterized by slight relief and broad areas of level lands, there are a few regions of sufficient ruggedness to merit special mention and to attract the attention of tourists who wish to visit those portions of Illinois presenting scenery in striking contrast to the flat prairie lands of the rich agricultural districts. The state-aid system of good roads leads into every county of the state, and these picturesque regions will thus be opened to automobile parties for easy and profitable exploration.
The Ozark Ridge.—The Ozark Highland, Of which the Illinois Ozarks is a spur, is the most conspicuous elevated region between the Appalachian and the Rocky mountains. Its area of 50,000 square miles is shared by five states, with 33,000 square miles in southern Missouri, 13,000 in northern Arkansas, 3,000 in northeastern Oklahoma, and the remaining 1,000 square miles in southern Illinois and southeastern Kansas, the area in Illinois being larger than that in Kansas. The Ozark Ridge of southern Illinois is the most conspicuous single topographic feature in the state. It extends eastward across the state from the flood plains of the I3ig Muddy and Mississippi rivers in Jackson and Union counties to the flood plains of the Saline and Ohio rivers in Gallatin and Hardin counties, a distance of about 70 miles. Its northern edge extends east-west in the southern portions of Jackson, William son, Saline, and Gallatin counties, while the southern edge is found along a more irregular line across the southern portions of Union, Johnson, Pope, and Hardin counties. To the north lie the lower lands of the Big :Muddy and Saline river basins, and to the south the bottom lands of the Ohio, Big Bay, and Cache rivers. The axis of the ridge thus lies along an east west line in the northern portions of the four counties last named. A rectangle 70 miles in east-west extent and 12 miles in north-south dimension includes nearly all of the highlands of the Ozark Ridge in Illinois and considerable areas of lowlands along the stream valleys. The area, more than 600 feet above sea-level, is nearly 400 square miles in extent, and the total area, more than 500 feet in elevation, is about twice as large. The crest of the ridge, in at least four areas, rises above 700 feet, with the culminating peak, Williams' Hill in north eastern Pope County, rising to an altitude of 1,065 feet above sea-level, and more than 700 feet above the Ohio River 12 miles distant.