East Division Street Bridge, Spanning North Branch Canal at West Division Street, Chicago, Cook County, IL

Significance: When Chicago became a major commercial and industrial center after the Civil War, the most common American drawbridge was the swing bridge, horizontally rotating on a center pier to open two navigation channels. The center pier, however, became a navigational hazard for the ever-larger craft of the late nineteenth century, especially on crowded, narrow waterways such as the Chicago River. During the late 1890s, Chicago City Engineer John Ericson initiated a planning study to find an alternative to the swing span. Finding inspiration in the 1894 Tower Bridge in London, England, the municipal engineering staff developed a new movable-bridge design. The type was known as a double-leaf bascule, French for "seesaw." Each movable leaf rotated vertically on a fixed, horizontal steel axle, or trunnion, leaving the entire river channel open for shipping. With the front of each leaf counterbalanced by weights at the rear, relatively small motors could open and close the span. Completed in 1903, the East Division Street Bridge embodied the earliest version of the city-sponsored bascule design selected for construction.
Survey number: HAER IL-147
Building/structure dates: 1903