DuSable Bridge

The Michigan Avenue Bridge has a north–south orientation, spanning the main stem of the Chicago River between the Near North Side and Loop community areas of Chicago. Its northern portal lies at the foot of the Magnificent Mile, between the Wrigley Building and Tribune Tower. Its southern portal is at the intersection of Michigan Avenue and Wacker Drive, overlooked by the London Guarantee Building and 333 North Michigan. The neighboring bridges are Columbus Drive Bridge to the east and Wabash Avenue Bridge to the west. The bridge is situated in a historically significant area. The northern end of the bridge covers part of the Jean Baptiste Point Du Sable Homesite, which is commemorated by a National Historic plaque in Pioneer Court. The southern half of the bridge passes over the site of Fort Dearborn, which was constructed in 1803. The Fort is commemorated by a large relief above the entrance of the London Guarantee Building, and brass markers positioned in the sidewalks on the south side of the bridge delineate the posited outline of the original blockhouse. ==Name==

The historical significance of the location has been used as the basis for a number of proposals to rename the bridge. In 1921 the Chicago Historical Society suggested that the bridge should be named Marquette–Joliet Bridge, and in 1939 it was proposed to rename the bridge as Fort Dearborn Bridge. These proposals were not adopted. In October 2010, the bridge was renamed DuSable Bridge in honor of Jean Baptiste Point du Sable, Chicago's first permanent resident. A fur trader of African descent who married into the Potawatomi tribe, he established a permanent homestead and trading post near the mouth of the Chicago River in the 1780s. ==History==

, looking north from Grant Park A boulevard to link the parks on Chicago's north and south sides was proposed as early as 1891. In 1903 an editorial in the Chicago Tribune proposed a new bascule bridge across the river at Michigan Avenue. Other plans suggested that the bridge should be a replica of the Pont Alexandre III that spans the Seine in Paris, or that, rather than constructing an entirely new bridge, the existing Rush Street bridge should be double-decked. Plans for the boulevard and the construction of a Michigan Avenue Bridge were further elaborated upon in Daniel Burnham's 1909 Plan of Chicago. In 1911 a plan was selected that included the widening of Michigan Avenue from Randolph Street to the river, replacing the Rush Street bridge with a new bridge at Michigan Avenue and the construction of a double-decked boulevard along Pine Street as far as Ohio Street. An ordinance to fund construction was passed in 1913, but was declared void by the Supreme Court of Illinois. A second ordinance was passed in 1914, but legal battles continued until the end of 1916. Construction finally started on April 15, 1918, and the bridge was officially opened in a ceremony on May 14, 1920. It was also designated as a Chicago Landmark on October 2, 1991. In 2009 the sidewalks and railings on the bridge were replaced, and the bridge was repainted; the design of the new ornamental railings was based on the original 1920 design for the bridge's railings, replacing more utilitarian ones that had been substituted at a later date. ==Design and operation==

Michigan Avenue Bridge is a double-leaf, double-deck, fixed counterweight, trunnion bascule bridge. At the time of construction it was believed to be the first double-deck bridge ever built to have roadway on both levels; faster non-commercial traffic using the upper deck and slower commercial traffic that served the various industries and docks in the vicinity of the river using the lower deck. The counterweights are below the level of the lower deck and when the bridge is opened they swing down into reinforced concrete tailpits that descend below the surface of the river. Each of the two tailpits is supported on nine cylindrical foundation piers. One of these piers was sunk to bedrock, below the river surface, the other 17 piers are sunk to the hardpan, which is below the water level. The Michigan Avenue Bridge is made of steel. The bridge can carry about 30,000 people daily. The bridge abutments and the facing of the bridge tender houses are made of Bedford stone. There are four bridge tender houses: the northwest and southeast bridgehouses house the controls for operating the bridge; the northeast and southwest bridgehouses are purely decorative. Two motors open and close each of the bridge leaves. Originally the bridge was staffed 24 hours a day, and opened up to 3,000 times a year to allow ships through, but since the 1970s bridge lifting has been scheduled in the spring and fall, when the bridge is raised twice weekly to allow sailboats to pass between Lake Michigan and inland boat yards where they are stored for the winter. ==Decoration==

In 1928, sculptures depicting scenes from Chicago's history were added to the outward-facing walls of the four bridgehouses. The sculptures on the northern bridgehouses were commissioned by William Wrigley Jr. and made by James Earle Fraser: The Discoverers depicts Louis Joliet, Jacques Marquette, René-Robert Cavelier, Sieur de La Salle and Henri de Tonti; The Pioneers depicts John Kinzie leading a group through the wilderness. The sculptures on the southern bridgehouses were commissioned by the Benjamin F. Ferguson Monument Fund, and are by Henry Hering: Defense depicts Ensign George Ronan in a scene from the 1812 Battle of Fort Dearborn; Regeneration depicts workers rebuilding Chicago after the Great Chicago Fire of 1871. The bridge is also bedecked with 28 flagpoles, usually flying the flags of the United States, Illinois and Chicago. On special occasions other banners may be displayed. ==McCormick Bridgehouse & Chicago River Museum==

The southwest bridgehouse has been converted into a museum, with its entrance off the Chicago Riverwalk. The McCormick Bridgehouse & Chicago River Museum is a 5-floor, museum that opened on June 10, 2006; it is named for Robert R. McCormick, formerly owner of the Chicago Tribune and president of the Chicago Sanitary District. and includes exhibits on the history of the Chicago River and the bridge. Visitors are also allowed to access the bridge's gear room; during the spring and fall bridge lifting, visitors can see the bridge gears in operation as the leaves are raised and lowered. Chicago Tribune cultural arts writer Steve Johnson called the museum's gear room, where the DuSable Bridge mechanics can be viewed working, "a little chamber of heaven for infrastructure nerds." == See also ==