The Cortland Street

Drawbridge A drawbridge or draw-bridge is a type of moveable bridge typically at the entrance to a castle or tower surrounded by a moat. In some forms of English, including American English, the word ''drawbridge'' commonly refers to all types of moveable ...

(originally known as the Clybourn Place drawbridge) over 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 ...

is the original Chicago-style fixed-trunnion bascule bridge, designed by John Ericson and Edward Wilmann. When it opened in 1902, on

Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive Map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = List of sovereign states, Count ...

's north side, it was the first such bridge built in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

. The bridge was a major advance in American

movable bridge A moveable bridge, or movable bridge, is a bridge that moves to allow passage for boats or barges. In American English, the term is synonymous with , and the latter is the common term, but drawbridge can be limited to the narrower, historical d ...

engineering, and was the prototype for over 50 additional bridges in Chicago alone. The bridge was designated as an ASCE

Civil Engineering Landmark Civil may refer to: *Civic virtue, or civility *Civil action, or lawsuit * Civil affairs *Civil and political rights *Civil disobedience *Civil engineering *Civil (journalism), a platform for independent journalism *Civilian, someone not a membe ...

in 1981, and a Chicago Landmark in 1991.

Design

This is the bridge type for which Chicago engineers are most well-known. The trunnion bascule has two bridge leaves with pivots on the opposing riverbanks and are raised on large trunnion bearings by large counterweights which offset the weight of the leaves. They take their names from the French word ''bascule'', meaning ''seesaw'', and the counterweights. Unlike most of the subsequent bascule bridges of Chicago, the gear rack that moves this bridge is visible above the roadway, on the curved arcs at each end of the superstructure.

History

The bridge was built under the supervision of Mayor

Carter Harrison, Jr. Carter Henry Harrison IV (April 23, 1860 – December 25, 1953) was an American newspaper publisher and Democratic politician who served a total of five terms as mayor of Chicago (1897–1905 and 1911–1915) but failed in his attempt to become ...

, and Frederick W. Block, the Commissioner of Public Works. This is the second bridge built on this site, which replaced a

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 p ...

with a mid-river pier supporting the swing span. The current bridge eliminated the need for the mid-river pier, allowing more room in the shipping channel. While the machinery of the current bridge is intact, the bridge is no longer operable and the leaves are clamped together. The bridge was traversed by

streetcar A tram (called a streetcar or trolley in North America) is a rail vehicle that travels on tramway tracks on public urban streets; some include segments on segregated right-of-way. The tramlines or networks operated as public transport ...

s of Line 73-Armitage Avenue, in addition to other traffic until February 25, 1951. The following day the bridge was temporarily closed for repairs and the

Chicago Transit Authority The Chicago Transit Authority (CTA) is the operator of mass transit in Chicago, Illinois, United States, and some of its surrounding suburbs, including the trains of the Chicago 'L' and CTA bus service. In , the system had a ridership of , ...

(CTA) substituted buses for streetcars east of the bridge, subsequently abandoning the remainder of the Armitage Avenue streetcar line in June. Electric trolley buses also crossed the bridge, starting on February 1, 1953, when CTA replaced the

motor bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for ...

es on route 73. Trolley buses operated until October 15, 1966, when the agency converted the route to diesel buses. The Cortland Street Bridge is currently used for two-way vehicle traffic, pedestrian, and bicycle traffic.

References

External links

* {{Chicago Landmark transportation Bridges in Chicago Bridges completed in 1902 Bascule bridges in the United States Historic American Engineering Record in Illinois Historic Civil Engineering Landmarks Chicago Landmarks Road bridges in Illinois Steel bridges in the United States

Design

History

See also

References

External links