The Michigan Avenue Bridge is a bascule bridge that carries Michigan Avenue across the main stem of the Chicago River. The bridge was constructed between 1918 and 1920 as part of a plan to link Chicago's south side and north side parks with a grand boulevard. It is an early example of a fixed trunnion bascule bridge, which later became widely known as a "Chicago style bascule." It is part of the Michigan–Wacker Historic District and is a Chicago Landmark.
Michigan Avenue Bridge is a double-leaf, double-deck, fixed counterweight, trunnion bascule bridge. It has four bascule leaves such that it functions as two parallel bridges that can be operated independently of one another; at the time of construction bridges in the Chicago River were frequently struck by vessels, and this duplex arrangement allows for leaves damaged in such a collision to be opened for repair without needing to completely close the bridge to traffic. The counterweights are below the level of the lower deck and when the bridge is opened they swing down into 40-foot deep reinforced concrete tailpits that descend 34.5 feet below the surface of the river.
In Spring and Fall, 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. Two 108-horsepower motors open and close each of the 3,750-ton bridge leaves.
Photo captured on July 2, 2010.
New photos posted on most Mondays through Thursdays.
All photos are copyrighted and may not be reproduced or distributed without my expressed, written consent.