THE TOPOGRAPHY AND HYDROGRAPHY OF ILLINOIS XXXIX 



waters, it has always been an especially important stream. To 

 the early explorers, traders, and missionaries, as well as to the 

 aborigines before them, it furnished, together with the Des 

 Plaines and the Chicago portage, one of the most frequently 

 traveled waterways through the interior of the country, and 

 the settlements along its banks were among the earliest in the 

 state. At a later period it became a useful commercial high- 

 way, a function which it now seems certain to resume, at no 

 distant day, on a scale of national importance. Its yield of 

 fishery products is greater than that of all the other waters of 

 the state combined,* and it serves an indispensable purpose to 

 the City of Chicago and to the principal towns upon its banks 

 in conveying away their liquid wastes, which it renders harmless 

 by decomposition an$ useful by converting them more or less 

 directly into a food supply for fishes. 



The Illinois may be regarded as in many respects a typical 

 stream of the central prairies of the Mississippi Valley, peculiar 

 now, however, in the enormous amount of sewage which it car- 

 ries mainly received from Chicago by way of the drainage 

 canal together with the large amount of refuse from distilleries 

 and cattle-yards along its course. It flows, in most of its length, 

 down the bed of an ancient outlet of Lake Michigan, by which 

 the waters of that lake were conveyed to the Mississippi River. 

 Within this bed it has excavated its own present channel, with 

 its present bottom-lands or " first bottoms," subject to overflow 

 at high water. Its second bottoms, above the reach of high 

 water, are the flood-plain of the former outlet of the lake. This 

 ancient channel varies in width from l}/2 to 6 miles, or, if the 

 flood-plain of the older river be also included, to a maximum 

 width of 20 miles, the bluffs on either side ranging in altitude from 

 450 to 800 feet. The highest points of these bluffs are near Peoria, 

 and near the mouth of the river in Calhoun county. The water- 

 sheds bounding the river basin range in height from 700 to 1 ,000 

 feet above the sea, the average elevation being 600 or 700 feet. 



The length of the Illinois from its origin in the junction of the 

 Kankakee and the Des Plaines is approximately 273 miles; or, if 

 its longest tributary, the Kankakee, be added, the total is 413 

 miles. The length of the stream itself is 28 per cent, greater than 

 that of a straight line from its origin to its mouth an unusually 

 small percentage for the tributaries of the Mississippi. It takes, 



*In 1899 the total value of the product of the fisheries of Illinois was $616,452, and that 

 of the fisheries of the Illinois River was $382,372. 



