In 1899, engineers from the City of Chicago's Division of Bridges and Viaducts performed a survey of moveable bridge design in the U.S. and Europe. Their study led to the conclusion that the unusual trunnion bascule design would best meet their needs.
The Cortland Street Drawbridge was the first trunnion bascule bridge constructed in the United States. In operation longer than any bascule bridge of its kind, it was a model for 53 of Chicago's 54 moveable bridges. Although no longer in use, the bridge stands as a symbol of the pioneering engineering efforts that led to modern-day bascule bridge design.