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 b ...
(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). The river is one of the reasons for Chicago's geographic importance: the related Chic ...
is the original Chicago-style
fixed-trunnion bascule bridge, designed by John Ericson and Edward Wilmann.
When it opened in 1902, on
Chicago
Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...
's north side, it was the first such bridge built in the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
. 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 ...
engineering, and was the prototype for over 50 additional bridges in Chicago alone.
The bridge was designated as an
ASCE
The American Society of Civil Engineers (ASCE) is a tax-exempt professional body founded in 1852 to represent members of the civil engineering profession worldwide. Headquartered in Reston, Virginia, it is the oldest national engineering soci ...
Civil Engineering Landmark in 1981, and a
Chicago Landmark
Chicago Landmark is a designation by the Mayor and the City Council of Chicago for historic sites in Chicago, Illinois. Listed sites are selected after meeting a combination of criteria, including historical, economic, architectural, artist ...
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., and Frederick W. Blocki, 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 can be rotated horizontally around a vertical axis. It has as its primary structural support a vertical locating pin and support ring, usually at or near to its center of gravit ...
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 (also known as a streetcar or trolley in Canada and the United States) is an urban rail transit in which vehicles, whether individual railcars or multiple-unit trains, run on tramway tracks on urban public streets; some include s ...
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 public transport, mass transit in Chicago, Illinois, United States, and some of its suburbs, including the trains of the Chicago "L" and List of Chicago Transit Authority bus routes, CTA bu ...
(CTA) substituted buses for streetcars east of the bridge, subsequently abandoning the remainder of the Armitage Avenue streetcar line in June.
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 motor vehicle that carries significantly more passengers than an average car or van, but fewer than the average rail transport. It is most commonly used ...
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.
See also
*
References
External links
*
{{Chicago Landmark transportation
Bridges in Chicago
Bridges completed in 1902
Bascule bridges in Illinois
Historic American Engineering Record in Illinois
Historic Civil Engineering Landmarks
Chicago Landmarks
Road bridges in Illinois
Steel bridges in the United States