About The Bridge
PHOTO ©2013 JAMES S. PHILLIPS, CHICAGOLOOPBRIDGES.COM
In the 1920s, the Michigan Avenue Bridge would lift more than 3,000 times a year. Today, it lifts approximately 40 times a year. On select bridge lift dates, visitors can view the bridgeworks in motion at the Bridgehouse Museum.
Visit our Bridge Lifts page for details.
The Michigan Avenue Bridge is the first double-deck, double-leaf, fixed trunnion bascule bridge ever built. First conceived by architect Daniel Burnham in his 1909 “Plan for Chicago,” the Michigan Avenue Bridge was designed as a gateway between Chicago’s north side and south side. Edward Bennett designed the bridge and its four bridgehouses following the Beaux-Arts style and in keeping with Burnham’s concept. Engineers Hugh E. Young, Thomas Pihlfeldt and William A. Mulcahy were instrumental in its construction, which began in 1918.
The bridge was opened for traffic in 1920. The bridgehouses final ornamental touch was added in 1928, when bas-relief sculptures depicting scenes from Chicago history were installed. The Bridgehouse Museum is adorned by the sculpture titled Defense by Henry Hering, depicting a scene from the 1812 Battle of Fort Dearborn. The southern end of the bridge neighbors the original Fort Dearborn site.
The Michigan Avenue Bridge has indeed become a much-used connection between Chicago’s north and south, just like Burnham had envisioned. Today, thousands of people traverse the bridge daily. The bridge, along with its bridgehouses, was designated a Chicago Landmark in 1991 by the City of Chicago and the State of Illinois. In 2010, the bridge was officially renamed DuSable Bridge in honor of Chicago’s first permanent resident, Jean Baptiste Point DuSable, whose homesite abuts the northern end of the bridge.
How It Works
The Michigan Avenue Bridge is a fixed trunnion bascule bridge, a type known throughout the world as a “Chicago-type bascule bridge.” A bascule bridge is a drawbridge hinged with a counterweight that continuously balances the leaf (or long arm that crosses the river). Trunnion refers to the pin and supporting bearing that forms the hinge, allowing the bridge leaves to move up and down. The balance of the approximately 4,100-ton bridge leaf and 12,000-ton counterweight of the bridge is so precise, it only takes a 108-horsepower motor to open and close each leaf. The motor powers a series of gears, the last of which is called a pinion gear. The pinion gear grasps grooves mounted on the bridge counterweight, pushing the counterweight side downwards into a counterweight pit and lifting the bridge’s long arm up in the air. An engineering wonder even today, the bridge’s massive gears are viewable from inside the Bridgehouse Museum.
