A view of the Chicago River from the South Branch, looking toward the Main Stem (right) and the North Branch (upper left) at Wolf Point
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.
Kayakers take a break at Wolf Point with 333 West Wacker, Lake Street Bridge and the south skyline in the background
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.
The North Branch continues southwards through Niles, entering the city of Chicago near the intersection of Milwaukee Avenue and Devon Avenue, from where it serves as the boundary of the Forest Glen with Norwood Park and Jefferson Park. This stretch of the river meanders in a south-easterly direction, passing through golf courses and forest preserves until it reaches Foster Avenue, where it passes through residential neighborhoods on the north side of the Albany Park community area. In River Park the river meets the North Shore Channel, a drainage canal built between 1907 and 1910 to increase the flow of the North Branch and help flush pollution into the Chicago Sanitary and Ship Canal. From the confluence with the North Shore Channel south to Belmont Avenue the North Branch flows through mostly residential neighborhoods in a man-made channel that was dug to straighten and deepen the river, helping it to carry the additional flow from the North Shore Channel.
South of Belmont the North Branch is lined with a mixture of residential developments, retail parks, and industry until it reaches the industrial area known as the Clybourn Corridor. Here it passes beneath the Cortland Street Drawbridge, which was the first 'Chicago-style' fixed-trunnion bascule bridge built in the United States, and is designated as an ASCE Civil Engineering Landmark and a Chicago Landmark.
At North Avenue, south of the North Avenue Bridge, the North Branch divides, the original course of the river makes a curve along the west side of Goose Island, whilst the North Branch Canal cuts off the bend, forming the island. The North Branch Canal—or Ogden's Canal—was completed in 1857, and was originally 50 feet (15 m) wide and 10 feet (3.0 m) deep allowing craft navigating the river to avoid the bend. The 1902 Cherry Avenue Bridge, just south of North Avenue, was constructed to carry the Chicago, Milwaukee and St. Paul Railway onto Goose Island. It is a rare example of an asymmetric bob-tail swing bridge and was designated a Chicago Landmark in 2007. From Goose Island the North Branch continues to flow south east to Wolf Point where it joins the Main Stem.
The source of the Main Stem of the Chicago River is Lake Michigan. Water enters the river through sluice gates at the Chicago River Controlling Works with a small additional flow provided by the passage of boats between the river and Lake Michigan through the Chicago Harbor Lock. The surface level of the river is maintained at 0.5 to 2 feet (0.15 to 0.61 m) below the Chicago City Datum (579.48 feet [176.63 m] above mean sea level) except for when there is excessive storm run-off into the river or when the level of the lake is more than 2 feet below the Chicago City Datum. Acoustic velocity meters at the Columbus Drive Bridge and the T. J. O'Brien lock on the Calumet River monitor the diversion of water from Lake Michigan to the Mississippi River basin, which is limited to an average of 3,200 cubic feet (91 m3) per second per year over the 40-year period from 1980 to 2020.
View west along the Main Stem of the Chicago River from the Outer Drive Bridge, 2009
The Main Stem flows 1.5 miles (2.4 km) west from the controlling works at Lake Michigan; passing beneath the Outer Drive, Columbus Drive, Michigan Avenue, Wabash Avenue, State Street, Dearborn Street, Clark Street, La Salle Street, Wells Street, and Franklin Street bridges en route to its confluence with the North Branch at Wolf Point. At McClurg Court it passes the Nicholas J Melas Centennial Fountain, which was built in 1989 to celebrate the 100th anniversary of the Metropolitan Water Reclamation District of Greater Chicago; between May and October the fountain sends an arc of water over the river for ten minutes every hour. On the north bank of the river, near the Chicago Landmark Michigan Avenue Bridge, is Pioneer Court, which marks the site of the homestead of Jean Baptiste Point du Sable who is recognized as the founder of Chicago. On the south bank of the river is the site of Fort Dearborn, an army fort, first established in 1803. Notable buildings surrounding this area include the NBC Tower, the Tribune Tower, and the Wrigley Building. The river turns slightly to the south west between Michigan Avenue and State Street, passing the Trump International Hotel and Tower, 35 East Wacker, and 330 North Wabash. Turning west again the river passes Marina City, the Reid, Murdoch & Co. Building, and Merchandise Mart, and 333 Wacker Drive.
Since the early 2000s, the south shore of the Main Stem has been developed as the Chicago Riverwalk. It provides a linear, lushly landscaped park intended to offer a peaceful escape from the busy Loop and a tourist attraction. Different sections are named Market, Civic, Arcade, and Confluence. The plans reflect ideas first proposed by the Burnham Plan as early as 1909.
The confluence of the North Branch (upper right) and Main Stem (lower right) of the Chicago River at Wolf Point to form the South Branch of the Chicago River (left)
Before reversal, the South Branch generally arose with joining forks in the marshy area called Mud Lake to flow to where it met the North Branch at Wolf Point forming the main branch. Since reversal, the source of the South Branch of the Chicago River is the confluence of the North Branch and Main stem at Wolf Point. From here the river flows south passing the Lake Street, Randolph Street, Washington Street, Madison Street, Monroe Street, Adams Street, Jackson Boulevard, Van Buren Street, Ida B. Wells Drive, and Harrison Street bridges before leaving the downtown Loop community area. Notable buildings that line this stretch of the river include the Boeing Company World Headquarters, the Civic Opera House, the Chicago Mercantile Exchange, Union Station and Willis Tower.
The river continues southwards past railroad yards and the St. Charles Air Line Bridge. Between Polk and 18th Streets the river originally made a meander to the east; between 1927 and 1929 the river was straightened and moved 1⁄4 mile (0.40 km) west at this point to make room for a railroad terminal. The river turns to the southwest at Ping Tom Memorial Park where it passes under the Chicago Landmark Canal Street railroad bridge. The river turns westward where it is crossed by the Dan Ryan Expressway; these immovable bridges have a clearance of 60 feet (18 m) requiring large ships that pass underneath to have folding masts.
At Ashland Avenue the river widens to form the U.S. Turning Basin, the west bank of which was the starting point of the Illinois and Michigan Canal. Prior to 1983, this was where the US Coast Guard Rules of the Road, Great Lakes ended & Rules of the Road, Western Rivers began. Since 1983, there is just a single Inland Navigational Rules passed by Congressional Act in 1980 (Public Law 96-591). At the basin the river is joined by a tributary, the South Fork of the river, which is commonly given the nickname Bubbly Creek. A bridge used to span the South Fork at this point that was too low for boats to pass meaning that their cargo needed to be unloaded at the bridge, and the neighborhood at its east end became known as Bridgeport. The river continues to the south west, entering the Chicago Sanitary and Ship Canal at Damen Avenue. The original West Fork of the South Branch, which before 1935 led towards Mud Lake and the Chicago Portage, has been filled in; a triangular intrusion into the north bank at Damen Avenue marks the place where it diverged from the course of the canal. From there, the water flows down the canal through the southwest side of Chicago and southwestern suburbs and, in time, into the Des Plaines River between Crest Hill on the west and Lockport on the east, just north of the border between Crest Hill and Joliet, Illinois, eventually reaching the Gulf of Mexico.
The United States Geological Survey monitors water flow at a number of sites in the Chicago River system. Discharge from the North Branch is measured at Grand Avenue; between 2004 and 2010 this averaged 582 cubic feet (16.5 m3) per second. During the winter months as much as 75% of the flow in the North Branch is due to the discharge of treated sewage from the North Side Water Reclamation Plant into the North Shore Channel. Flow on the Main Stem is measured at Columbus Drive; between 2000 and 2006 this averaged 136 cubic feet (3.9 m3) per second.