<P> The River is also noteworthy for its natural and man - made history . In 1887, the Illinois General Assembly, partly in response to concerns arising out of an extreme weather event in 1885 that threatened the city's water supply, decided to reverse the flow of the Chicago River through civil engineering by taking water from Lake Michigan and discharging it into the Mississippi River watershed . In 1889, the Illinois General Assembly created the Chicago Sanitary District (now The Metropolitan Water Reclamation District) to replace the Illinois and Michigan Canal, which had become inadequate to carry the city's increasing sewage and commercial navigation needs, with the Chicago Sanitary and Ship Canal, a much larger waterway . The District completed this man - made hydrologic connection between the Great Lakes and Mississippi watershed in 1900 by reversing the flow of the Main Stem and South Branch of the river using a series of canal locks, and increasing the river's flow from Lake Michigan, causing it to empty into the new Canal . In 1999, this system was named a' Civil Engineering Monument of the Millennium' by the American Society of Civil Engineers (ASCE). </P> <P> The river is memorialized, in part, by two horizontal blue stripes on the Municipal Flag of Chicago . The river also serves as inspiration for one of Chicago's ubiquitous symbols: a three - branched, Y - shaped symbol (called the municipal device) is found on many buildings and other structures throughout Chicago; it represents the three branches of the Chicago River . </P> <P> When it followed its natural course, the North and South Branches of the Chicago River converged at Wolf Point to form the Main Stem, which jogged southward from the present course of the river to avoid a baymouth bar entering Lake Michigan at about the level of present - day Madison Street . Today, the Main Stem of the Chicago River flows west from Lake Michigan to Wolf Point, where it converges with the North Branch to form the South Branch, which flows southwest and empties into the Chicago Sanitary and Ship Canal . </P> <P> Early settlers named the North Branch of the Chicago River the Guarie River, or Gary's River, after a trader who may have settled the west bank of the river a short distance north of Wolf Point, at what is now Fulton Street . The source of the North Branch is in the northern suburbs of Chicago where its three principal tributaries converge . The Skokie River--or East Fork--rises from a flat area, historically a wetland, near Park City, Illinois to the west of the city of Waukegan . It then flows southward, paralleling the edge of Lake Michigan, through wetlands, the Greenbelt Forest Preserve and a number of golf courses towards Highland Park, Illinois . South of Highland Park the river passes the Chicago Botanic Gardens and through an area of former marshlands known as the Skokie Lagoons . The Middle Fork arises near Rondout, Illinois and flows southwards through Lake Forest and Highland Park . These two tributaries merge at Watersmeet Woods west of Wilmette . From there the North Branch flows south towards Morton Grove . The West Fork rises near Mettawa and flows south through Bannockburn, Deerfield, and Northbrook, meeting the North Branch at Morton Grove . In recognition of the work of Ralph Frese in promoting canoeing on and conservation of Chicago - area rivers, the forest preserve district of Cook County, Illinois has designated a section of the East Fork and North Branch from Willow Road in Northfield to Dempster Street in Morton Grove the Ralph Frese River Trail . </P>

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