For at least the past decade, it has been used as the backdrop for uncounted wedding photos, and in classic Chicago urban landscapes images. The Kinzie Street Railroad Bridge, a gawky piece of the built environment with its steel structure pointing skyward and imposing concrete counterweights in suspension, fascinates Chicagoans and visitors alike.
The single-leaf bascule bridge built by the Chicago & North Western Railway next to Kinzie Street has stood open by the fork of the Chicago River seemingly forever, flanked by River North Point and the surrounding skyscraper canyons. This well known, but little understood Chicago Icon draws attention and provokes so many questions like, “Why is this old bridge always open, and if it is not used, why not tear it down?”
Built in 1908, the current bridge is the fifth railroad bridge at this site, and was the world’s longest and heaviest single-leaf bascule bridge at the time it was built. It was designed by the Strauss Bascule Bridge Company, based on a patent by Joseph B. Strauss, the Chicago engineer who is best known as Chief Engineer for the Golden Gate Bridge crossing the San Francisco Bay.
This patented heel trunnion design was a favorite of the railroads. Trunion, or axle, is the engineering term describing the cylindrical steel ears upon which the entire bridge superstructure pivots. Two trunnions, one on each side of the bridge superstructure are held by bearings and supported by a short tower and foundation. The location of these trunnions very close to the heel or back edge of the bridge leaf lends it its name, and it operates similar to a trap door with massive concrete counterweights. The bridge superstructure and counterweights are connected through a steel parallelogram (shown by the dotted black lines), which changes shape during bridge operation. Perfectly balanced, the bridge is operated by two 50 horsepower electric motors that activate a pinion (or drive gear) that meshes with a racked strut to raise and lower the bridge.
When this bridge first opened, it carried some 373 trains per day, and within the first month was opened 983 times for an average of 31 lifts per day. Located just south of Chicago’s very first bridge at Kinzie Street, it is hard to imagine less than 200 years ago the early village of Chicago of a few hundred people of French and Indian decent occupying this low-lying swampy area.
In 1852 the Galena & Chicago Union, Chicago’s first railroad, constructed the city’s first railroad bridge here. The bridge connected to a new passenger and a freight terminal on the north bank of the main channel of the Chicago River. This spur of the railroad east of the North Branch stretching to the river mouth at Lake Michigan served passengers, freight, and numerous commercial customers on the north bank of the river.
By the middle of the 20th Century, heavy industry along the river was fleeing the city center and relocating to the Calumet River, collar counties, or overseas. By the beginning of the 21st Century only one commercial customer for this railroad spur remained. The Chicago Sun-Times, on the river between Wabash Avenue and Rush Street still received massive two to three-ton rolls of newsprint by rail. However in early 2001 production of the newspaper moved to a new facility at 2800 South Ashland Avenue and ended the need for this bridge and eastern railroad spur. Soon thereafter the old Sun-Times building was demolished and the site is now home to the Trump International Hotel and Tower, which opened on January 8, 2008.
Today the Kinzie Street Railroad Bridge remains open at the request of the U.S. Coast Guard, which has oversight of all national waterways, including the Chicago River’s main channel and North and South Branches between Belmont Avenue and South Ashland Avenue. As this bridge, when closed, is well below the later established 16 ½ foot river clearance, it remains locked in the open position. This allows recreational, tourist, and commercial traffic to move unhindered up and down the North Branch of the Chicago River.
In 2007, as one of a dozen railroad bridges it was granted Chicago Landmark status, which should ensure it remains standing for many years to come. In the past couple decades various proposals for additional bus and transit routes incorporated the use of this bridge, however federal laws giving river traffic the right of way, and the bridge’s low clearance created additional impediments to adoption of these plans.
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