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Illinois River Cruises

Geology

South of Hennepin, the Illinois River is following the ancient channel of the Mississippi River. The Illinoian Stage, about 300,000 to 132,000 years ago, blocked the Mississippi near Rock Island, diverting it into its present channel. After the glacier melted, the Illinois River flowed into the ancient channel. The Hennepin Canal roughly follows the ancient channel of the Mississippi upstream of Rock Island.

The modern channel of the Illinois River was shaped in a matter of days by the Kankakee Torrent. During the melting of the Wisconsin Glacier about 10,000 years ago, a lake formed in present-day Indiana, comparable to one of the modern Great Lakes. The lake formed behind the terminal moraine of a substage of that glacier. Melting ice to the north eventually raised the level of the lake so that it overtopped the moraine. The dam burst, and the entire volume of the lake was released in a very short time, perhaps a few days.

Because of the manner of its formation, the Illinois River runs through a deep canyon with many rock formations. It has an “underutilised channel,” one far larger than would be needed to contain any conceivable flow in modern times.

Vacation Cruises

The Illinois River offers vacation cruises unlike any other river in the world. The rich history, beautiful scenery, and abundant wildlife all make the Illinois River a true natural treasure.

The Spirit of Peoria offers overnight Illinois River cruises from May through October.

The Illinois Waterway System

The Illinois Waterway System operates with eight dams that hold back water to form pools that resemble long narrow lakes. These dams raise the water level, making the river deep enough for large rivercraft that require nine feet of water to operate. This arrangement creates a “stairway of water” which drops 163 feet from lake Michigan to the Mississippi River. Once below St. Louis, the Mississippi is naturally deep enough so there is no longer a need for dams.

Illinois River Facts

  • Length: 273mi (439km)
  • Source: Confluence of the Kankakee and Des Plaines Rivers, elevation 505ft (154m)
  • Mouth: Mississippi River, elevation 417ft (127m)
  • Average Discharge: 23,200ft3/s (657m3/s)
  • Drains approximately 30,000 square miles of land and its drainage extends slightly into Wisconsin and Indiana.
  • Forms the greater part of the Illinois Waterway, which links the Great Lakes with the Mississippi.
  • Chief city on the river is Peoria.
  • Scientists have studied the geology and biology of the Illinois River for over 100 years—leading some to call it the “most studied river in the world.”
  • Illinois River wildlife includes: Eastern bluebird, Henslow sparrow, American bittern, black-crowned night heron, black and sora rails, bald eagle, river otter, muskrat, beaver, mink, bog lemming, prairie king and western ribbon snakes, plains leopard, and northern cricket frogs.

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