Michigan Avenue Bridge (looking south past Wacker Drive)
1954 / 2012
b/w photo by Jeanette Archie
Just after the turn of the century, Daniel Burnham, one of Chicago’s master architects, recognized the importance and significance in connecting north and south Michigan Avenue over the Chicago River. True to his 1909 Chicago Plan and designed by Edward Bennett, construction on the bridge began in 1917. It took three years to build the bascule trunnion bridge, and in 1920 opened to marching bands and much fanfare.
Due to its two levels, the Michigan Avenue Bridge is actually a double bascule trunnion. Bascule is French for “seesaw” and through the use of the trunnion bearings the counterweights continuously balance the span, or “leaf” throughout the upward movement. The leaves in this case are the two sections of Michigan Avenue. The balance of the leaves is so precise, it takes only two small 108-horsepower motors to open and close each of the 3,750-ton bridge leaves.
Aside from the mechanics, however, it’s the bas-relief sculptures on the bridge that make it one of the most photographed sights in Chicago. The sculptures depict significant events in Chicago’s early history. Today, the Michigan Avenue Bridge is traversed daily by thousands of workers, shoppers and visitors.
On the side….
The first bascule bridge was built in Chicago on Cortland Avenue in 1902.