Cortland Street Drawbridge

The Cortland Street Drawbridge (originally known as the Clybourn Place drawbridge) over the Chicago River is the original Chicago-style fixed-trunnion bascule bridge, designed by John Ericson and Edward Wilmann. When it opened in 1902, on Chicago's north side, it was the first such bridge built in the United States. The bridge was a major advance in American movable bridge engineering, and was the prototype for over 50 additional bridges in Chicago alone. The bridge was designated as an ASCE Civil Engineering Landmark in 1981, and a Chicago Landmark in 1991.DesignThis 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.HistoryThe bridge was built under the supervision of Mayor Carter Harrison, Jr. and Frederick W. Block, the Commissioner of Public Works.