The Canal Street railroad bridge (or Pennsylvania Railroad bridge) is a

vertical-lift bridge A vertical-lift bridge or just lift bridge is a type of movable bridge in which a span rises vertically while remaining parallel with the deck. The vertical lift offers several benefits over other movable bridges such as the bascule and swin ...

across the south branch of the

Chicago River The Chicago River is a system of rivers and canals with a combined length of that runs through the city of Chicago, including its center (the Chicago Loop). Though not especially long, the river is notable because it is one of the reasons for ...

Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive Map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = Country , subdivision_name ...

, Illinois. It was designated a

Chicago Landmark Chicago Landmark is a designation by the Mayor and the City Council of Chicago for historic sites in Chicago, Illinois, United States. Listed sites are selected after meeting a combination of criteria, including historical, economic, archite ...

on December 12, 2007.

Construction

The present bridge was constructed for the

Pennsylvania Railroad The Pennsylvania Railroad (reporting mark PRR), legal name The Pennsylvania Railroad Company also known as the "Pennsy", was an American Class I railroad that was established in 1846 and headquartered in Philadelphia, Pennsylvania. It was named ...

to replace a two-track

swing bridge A swing bridge (or swing span bridge) is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its center of gravity, about which the swing span (turning span) can then pi ...

at the same location. The necessity to allow both continued use of the swing bridge and unimpeded river traffic during building work complicated construction of the bridge. The chosen solution was to construct the bridge in the raised position above the old bridge, then demolish the old bridge once construction was completed. The bridge was designed by

Waddell & Harrington Waddell & Harrington was an American engineering company that designed bridges from 1907 to 1915. It was formed in 1907 as a partnership of John Alexander Low Waddell (1854–1938) and John Lyle Harrington (1868–1942) and was based in Kansas C ...

, and fabricated and erected by the Pennsylvania Steel Company. Construction of the south tower began on September 4, 1913. When the two towers were completed,

falsework Falsework consists of temporary structures used in construction to support a permanent structure until its construction is sufficiently advanced to support itself. For arches, this is specifically called centering. Falsework includes temporary su ...

for the main span was constructed in a fan shape that allowed the main span to be constructed in the raised position above the river. The bridge was built from steel and metal.

Operation

The bridge carries two railroad tracks across the Chicago River at an angle of about 40 degrees to the center line of the river. Upon completion, the main span could be raised in about 45 seconds. By 1916, each day the bridge was crossed by about 300 trains, and was raised for river traffic about 75 times.

Trivia

When it was constructed in 1914, its 1500-ton main span was the heaviest of any vertical lift bridge in the United States. It is the only vertical-lift bridge across the Chicago River.

Photo gallery

File:Canal Street bridges HAER IL-112-9.jpg File:Cermak Bridge Barge Passageway.jpg

References

External links