The Nature Conservancy in Illinois has chosen the Illinois River-Floodplain Ecosystem as one of its major conservation initiatives within our goal of preserving biodiversity in a manner which is economically and ecologically sustainable. The Illinois River, designated by the National Research Council as one of the few large rivers in the United States with a functioning fioodplain and floodpulse, provides an opportunity to evaluate how we can restore and maintain this river-floodplain system through the cooperation of a diverse group of individuals, agencies, and private interests. It is also an opportunity to provide a model for large river ecosystem management within the larger scope of the Upper Mississippi River Watershed. Because most of the watershed is within the state of Illinois, it is thought that efforts for planning and implementation can be streamlined within state and federal agency guidelines and mandates. Through a conservation planning process, the Conservancy has begun to identify areas within the river-floodplain system which have high quality aquatic and terrestrial communities that are maintained through functioning ecological processes of inundation and/or fire. Initial estimates have shown nearly 50 rare or imperiled (G1-G3) natural communities within the bluff to river areas of the main channel and its higher quality tributaries. Working with public and private partners in both the tributaries and main river-floodplain system, the Conservancy is developing a portfolio of sites which will capture the wide array of terrestrial and aquatic biodiversity within this unique system. Additionally, as a partner on the Illinois River Valley Partnership (IRVP), an effort led by Lieutenant Governor Bob Kustra, the Conservancy is working with a variety of state, federal and private partners representing agriculture, business, navigation, natural resources, and the scientific community to build a framework for preserving and restoring the Illinois River system. Through the interactions of these partners over the past year, the IRVP has begun to identify projects in which we can address both the ecological and economic concerns of maintaining a sustainable river system. As a model far large-scale public/private partnerships in conservation, the Illinois River will provide an unique example for researchers, conservation groups, landowners, communities, agencies and citizens to follow for future watershed management.