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In centuries past, rivers were the vital sustaining networks for indigenous populations, and later, European settlers. In Illinois, life and culture flourished along major rivers and at the confluence of their tributaries. As sources of transportation, food, drinking water, power, and habitat, healthy rivers have been the lifeblood of human and wildlife populations.  Today the Rock, Kishwaukee, Sugar and Pecatonica Rivers continue to be critical to our sustainable future.

A river is a dynamic entity; physically and ecologically. Not merely a conduit for water, but a complex system that does complex work. Rivers include not just the water flowing in their channels, but the food webs, nutrient cycles that operate within their beds and banks, the pools and wetlands that form on their floodplains, and the rich nutrient load they carry. Along with physical structures, river systems include communities of plant and animal species that are integral to their health. A river constantly evolves in response to changes in surrounding context, especially land use. Each of our region’s four rivers is unique due its river bed composition, water sources and volume, abundance and diversity of biological communities, presence and functionality of adjoining floodplains and wetlands, and impacts of past and present human activities in its watershed.

Anatomy of a River


The area of land that catches rain and snow and drains into a marsh, stream, river, lake or groundwater.


The beginning of a river is called its headwaters. Even if a river becomes huge and powerful, its headwaters often don’t start out that way. Some headwaters are springs that come from under the ground. Others are marshy areas fed by mountain snow. A river’s headwaters can be huge, with thousands of small streams that flow together, or just a trickle from a lake or pond. What happens in the headwaters is very important to the health of the whole river, because anything that happens upstream affects everything downstream.


A tributary is a river that feeds into another river, rather than ending in a lake, pond, or ocean. If a river is large, there’s a good chance that much of its water comes from tributaries.


The shape of a river channel depends on how much water has been flowing in it for how long, over what kinds of soil or rock, and through what vegetation. There are many different kinds of river channels – some are wide and  constantly changing, some crisscross like a braid, and others stay in one main channel between steep banks. The bends in a river called “meanders” are caused by the water taking away soil on the outside of a river bend and laying it down the inside of a river bend over time. Each kind of river channel has unique benefits to the environment.


The land next to the river is called the riverbank, and the streamside trees and other vegetation is sometimes called the “riparian zone.”  This is an important, nutrient-rich area for wildlife, replenished by the river when it floods. These areas also provide valuable services like protection from erosion during floods, and filtering polluted run-off from cities and farms.


The end of a river is its mouth, or delta. At a river’s delta, the land flattens out and the water loses speed, spreading into a fan shape. Usually this happens when the river meets an ocean, lake, or wetland. As the river slows and spreads out, it can no longer transport all of the sand and sediment it has picked up along its journey from the headwaters. It begins to lay down all the rocks, silt and driftwood it has been carrying along. Because these materials and nutrients help build fertile land, deltas have been called “cradles” of human civilization. Deltas are “cradles” for many other animals as well, providing breeding and nesting grounds for hundreds of species.

The Rock River

The Rock River that European settlers encountered was surrounded by fertile soils, large forests, and ran with clear sparkling water that supported thousands of species of insects, fish, turtles, frogs, mussels, birds and mammals.

The Kishwaukee River

The Kishwaukee River is considered to be one of the highest quality streams in Illinois due to its relatively clean water and the diversity of life it supports.

The Sugar River

The Sugar River is a high quality stream that flows through rural lands and native grasslands in southern Wisconsin and northern Illinois.

The Pecatonica River

The “Pec,” as it’s called sometimes by the locals, began forming several million years ago when the glaciers inched their way across southwest Wisconsin and northern Illinois, leaving their meltwaters to begin carving a region of broad, open ridgetops, deep valleys, and steep, wooded slopes.