THE TOPOGRAPHY AND HYDROGRAPHY OF ILLINOIS XXX1U 



of Louisiana, Mo. The deflection to the west is due to the 

 ridge of Illinoisan drift which follows the east border of the 

 stream and prevents it from entering the Illinois valley. The 

 river has a length of about 50 miles, rising at an altitude of 850 

 feet, draining 222 square miles, but falling 100 feet in its first 

 two miles, and below this averaging a fall of nearfy 7 feet to the 

 mile until it enters the Mississippi flats. The mouth is at an 

 altitude of about 430 feet. 



CAHOKIA RIVER 



Cahokia River rises in western Montgomery county, 

 crosses southern Macoupin county, and flows south and west, 

 emptying into the Mississippi near East St. Louis. It is about 

 50 miles long and drains an area of 360 square miles, rising at 

 an altitude of 640 feet, but falling 120 feet in the first 6 miles. 

 Below this it descends to 425 feet at Wanda, the point at which 

 it crosses the Mississippi bluffs and enters the bottom-lands of 

 that river. The mouth of the stream has an elevation of about 

 400 feet. The banks above Wanda are steep and abrupt, rising 

 100 feet or more on either side of the water. 



Illinois River System 



The Illinois and its branches drain an area of 28,100 square 

 miles, distributed among three states. Of this area, 24,940 

 square miles are in Illinois, extending in a broad band, 267 miles 

 long and averaging 100 miles in width, directly across the 

 center of the state in a northeast-southwest direction. From 

 the upper extremity of this band are two projections: one north 

 into Wisconsin, covering 1,020 square miles in that state; the 

 other east into Indiana, covering 3,140 square miles of its 

 northern portion. This eastern projection forms the basin of 

 the Kankakee River, while the northern one includes the basins 

 of the Fox and Des Plaines rivers. It is the union of the drainage 

 of these two projections which may be considered as the origin 

 of the Illinois, this name being applied to the river from the 

 point of junction of the Kankakee and the Des Plaines in eastern 

 Grundy county, Illinois. The Illinois flows westward for about 

 55 miles, turns rather abruptly southwest a little north of 

 Hennepin and follows this direction until it empties into the 

 Mississippi at the southern end of Calhoun county. The river 

 may readily be divided into two parts: the upper Illinois, con- 



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